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ï»żLast updated Save as PDF Page ID161838 Learning Objectives Describe the locations, charges, and masses of the three main subatomic particles. Determine the number of protons and electrons in an atom. Define atomic mass unit amu. Dalton's Atomic Theory explained a lot about matter, chemicals, and chemical reactions. Nevertheless, it was not entirely accurate, because contrary to what Dalton believed, atoms can, in fact, be broken apart into smaller subunits or subatomic particles. We have been talking about the electron in great detail, but there are two other particles of interest to us protons and neutrons. We already learned that J. J. Thomson discovered a negatively charged particle, called the electron. Rutherford proposed that these electrons orbit a positive nucleus. In subsequent experiments, he found that there is a smaller positively charged particle in the nucleus, called a proton. There is also a third subatomic particle, known as a neutron. Electrons Electrons are one of three main types of particles that make up atoms. Unlike protons and neutrons, which consist of smaller, simpler particles, electrons are fundamental particles that do not consist of smaller particles. They are a type of fundamental particle called leptons. All leptons have an electric charge of \-1\ or \0\. Electrons are extremely small. The mass of an electron is only about 1/2000 the mass of a proton or neutron, so electrons contribute virtually nothing to the total mass of an atom. Electrons have an electric charge of \-1\, which is equal but opposite to the charge of a proton, which is \+1\. All atoms have the same number of electrons as protons, so the positive and negative charges "cancel out", making atoms electrically neutral. Unlike protons and neutrons, which are located inside the nucleus at the center of the atom, electrons are found outside the nucleus. Because opposite electric charges attract one another, negative electrons are attracted to the positive nucleus. This force of attraction keeps electrons constantly moving through the otherwise empty space around the nucleus. The figure below is a common way to represent the structure of an atom. It shows the electron as a particle orbiting the nucleus, similar to the way that planets orbit the sun. However, this is an incorrect perspective, as quantum mechanics demonstrates that electrons are more complicated. Figure \\PageIndex{1}\ Electrons are much smaller than protons or neutrons. If an electron was the mass of a penny, a proton or a neutron would have the mass of a large bowling ball! Protons A proton is one of three main particles that make up the atom. Protons are found in the nucleus of the atom. This is a tiny, dense region at the center of the atom. Protons have a positive electrical charge of one \\left +1 \right\ and a mass of 1 atomic mass unit \\left \text{amu} \right\, which is about \ \times 10^{-27}\ kilograms. Together with neutrons, they make up virtually all of the mass of an atom. Neutrons Atoms of all elementsâexcept for most atoms of hydrogenâhave neutrons in their nucleus. Unlike protons and electrons, which are electrically charged, neutrons have no chargeâthey are electrically neutral. That's why the neutrons in the diagram above are labeled \n^0\. The zero stands for "zero charge". The mass of a neutron is slightly greater than the mass of a proton, which is 1 atomic mass unit \\left \text{amu} \right\. An atomic mass unit equals about \ \times 10^{-27}\ kilograms. A neutron also has about the same diameter as a proton, or \ \times 10^{-15}\ meters. As you might have already guessed from its name, the neutron is neutral. In other words, it has no charge whatsoever and is therefore neither attracted to nor repelled from other objects. Neutrons are in every atom with one exception, and they are bound together with other neutrons and protons in the atomic nucleus. Before we move on, we must discuss how the different types of subatomic particles interact with each other. When it comes to neutrons, the answer is obvious. Since neutrons are neither attracted to nor repelled from objects, they don't really interact with protons or electrons beyond being bound into the nucleus with the protons. Even though electrons, protons, and neutrons are all types of subatomic particles, they are not all the same size. When you compare the masses of electrons, protons, and neutrons, what you find is that electrons have an extremely small mass, compared to either protons or neutrons. On the other hand, the masses of protons and neutrons are fairly similar, although technically, the mass of a neutron is slightly larger than the mass of a proton. Because protons and neutrons are so much more massive than electrons, almost all of the mass of any atom comes from the nucleus, which contains all of the neutrons and protons. Table \\PageIndex{1}\ Properties of Subatomic Particles Particle Symbol Mass amu Relative Mass proton = 1 Relative Charge Location proton p+ 1 1 +1 inside the nucleus electron eâ Ă 10â4 â1 outside the nucleus neutron n0 1 1 0 inside the nucleus Table \\PageIndex{1}\ gives the properties and locations of electrons, protons, and neutrons. The third column shows the masses of the three subatomic particles in "atomic mass units." An atomic mass unit \\text{amu}\ is defined as one-twelfth of the mass of a carbon-12 atom. Atomic mass units \\text{amu}\ are useful, because, as you can see, the mass of a proton and the mass of a neutron are almost exactly \1\ in this unit system. Negative and positive charges of equal magnitude cancel each other out. This means that the negative charge on an electron perfectly balances the positive charge on the proton. In other words, a neutral atom must have exactly one electron for every proton. If a neutral atom has 1 proton, it must have 1 electron. If a neutral atom has 2 protons, it must have 2 electrons. If a neutral atom has 10 protons, it must have 10 electrons. You get the idea. In order to be neutral, an atom must have the same number of electrons and protons. Summary Electrons are a type of subatomic particle with a negative charge. Protons are a type of subatomic particle with a positive charge. Protons are bound together in an atom's nucleus as a result of the strong nuclear force. Neutrons are a type of subatomic particle with no charge they are neutral. Like protons, neutrons are bound into the atom's nucleus as a result of the strong nuclear force. Protons and neutrons have approximately the same mass, but they are both much more massive than electrons approximately 2,000 times as massive as an electron. The positive charge on a proton is equal in magnitude to the negative charge on an electron. As a result, a neutral atom must have an equal number of protons and electrons. The atomic mass unit amu is a unit of mass equal to one-twelfth the mass of a carbon-12 atom AnalisisElectron Beam Profile Constancy pada Pesawat Linac. Edi Guritna 1), Giner Maslebu 1,*), Nur Aji Wibowo 1), Muham mad Hidayatullah 2) 1) Program Studi Fisika dan Pendidikan Fisika Fundamental properties of atoms including atomic number and atomic mass. The atomic number is the number of protons in an atom, and isotopes have the same atomic number but differ in the number of pops up fairly often in the news. For instance, you might have read about it in discussions of nuclear energy, the Fukushima reactor tragedy, or the development of nuclear weapons. It also shows up in popular culture many superheroesâ origin stories involve radiation exposure, for instanceâor, in the case of Spider-Man, a bite from a radioactive spider. But what exactly does it mean for something to be radioactive?Radioactivity is actually a property of an atom. Radioactive atoms have unstable nuclei, and they will eventually release subatomic particles to become more stable, giving off energyâradiationâin the process. Often, elements come in both radioactive and nonradioactive versions that differ in the number of neutrons they contain. These different versions of elements are called isotopes, and small quantities of radioactive isotopes often occur in nature. For instance, a small amount of carbon exists in the atmosphere as radioactive carbon-14, and the amount of carbon-14 found in fossils allows paleontologists to determine their age. In this article, weâll look in more detail at the subatomic particles that different atoms contain as well as what makes an isotope number, atomic mass, and relative atomic massAtoms of each element contain a characteristic number of protons. In fact, the number of protons determines what atom we are looking at all atoms with six protons are carbon atoms; the number of protons in an atom is called the atomic number. In contrast, the number of neutrons for a given element can vary. Forms of the same atom that differ only in their number of neutrons are called isotopes. Together, the number of protons and the number of neutrons determine an elementâs mass number mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass property closely related to an atomâs mass number is its atomic mass. The atomic mass of a single atom is simply its total mass and is typically expressed in atomic mass units or amu. By definition, an atom of carbon with six neutrons, carbon-12, has an atomic mass of 12 amu. Other atoms donât generally have round-number atomic masses for reasons that are a little beyond the scope of this article. In general, though, an atom's atomic mass will be very close to its mass number, but will have some deviation in the decimal an elementâs isotopes have different atomic masses, scientists may also determine the relative atomic massâsometimes called the atomic weightâfor an element. The relative atomic mass is an average of the atomic masses of all the different isotopes in a sample, with each isotope's contribution to the average determined by how big a fraction of the sample it makes up. The relative atomic masses given in periodic table entriesâlike the one for hydrogen, belowâare calculated for all the naturally occurring isotopes of each element, weighted by the abundance of those isotopes on earth. Extraterrestrial objects, like asteroids or meteors, might have very different isotope and radioactive decayAs mentioned above, isotopes are different forms of an element that have the same number of protons but different numbers of neutrons. Many elementsâsuch as carbon, potassium, and uraniumâhave multiple naturally occurring isotopes. A neutral atom of Carbon-12 contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 six protons plus six neutrons. Neutral carbon-14 contains six protons, eight neutrons, and six electrons; its mass number is 14 six protons plus eight neutrons. These two alternate forms of carbon are isotopes are stable, but others can emit, or kick out, subatomic particles to reach a more stable, lower-energy, configuration. Such isotopes are called radioisotopes, and the process in which they release particles and energy is known as decay. Radioactive decay can cause a change in the number of protons in the nucleus; when this happens, the identity of the atom changes carbon-14 decaying to nitrogen-14.Radioactive decay is a random but exponential process, and an isotopeâs half-life is the period over which half of the material will decay to a different, relatively stable product. The ratio of the original isotope to its decay product and to stable isotopes changes in a predictable way; this predictability allows the relative abundance of the isotope to be used as a clock that measures the time from the incorporation of the isotope into a fossil to the example, carbon is normally present in the atmosphere in the form of gases like carbon dioxide, and it exists in three isotopic forms carbon-12 and carbon-13, which are stable, and carbon-14, which is radioactive. These forms of carbon are found in the atmosphere in relatively constant proportions, with carbon-12 as the major form at about 99%, carbon-13 as a minor form at about 1%, and carbon-14 present only in tiny amountsstart superscript, 1, end superscript. As plants pull carbon dioxide from the air to make sugars, the relative amount of carbon-14 in their tissues will be equal to the concentration of carbon-14 in the atmosphere. As animals eat the plants, or eat other animals that ate plants, the concentrations of carbon-14 in their bodies will also match the atmospheric concentration. When an organism dies, it stops taking in carbon-14, so the ratio of carbon-14 to carbon-12 in its remains, such as fossilized bones, will decline as carbon-14 decays gradually to nitrogen-14squared. After a half-life of approximately 5,730 years, half of the carbon-14 that was initially present will have been converted to nitrogen-14. This property can be used to date formerly living objects such as old bones or wood. By comparing the ratio of carbon-14 to carbon-12 concentrations in an object to the same ratio in the atmosphere, equivalent to the starting concentration for the object, the fraction of the isotope that has not yet decayed can be determined. On the basis of this fraction, the age of the material can be calculated with accuracy if it is not much older than about 50,000 years. Other elements have isotopes with different half lives, and can thus be used to measure age on different timescales. For example, potassium-40 has a half-life of billion years, and uranium-235 has a half-life of about 700 million years and has been used to measure the age of moon rockssquared. Andaboleh menentukan jumlah elektron dalam ion jika anda tahu cajnya. Kation membawa caj positif dan mempunyai lebih banyak proton daripada elektron. Anion membawa caj negatif dan mempunyai lebih banyak elektron daripada proton. Neutrons tidak mempunyai caj elektrik bersih, jadi bilangan neutron tidak penting dalam pengiraan.Seorang filsuf terdahulu yang berasal dari Yunani Demokritus 460-370 SM menyatakan bahwa semua materi terdiri dari partikel-partikel kecil yang tidak dapat dibagi lagi yang disebut sebagai atomos yang berarti âtidak dapat dibagiâ atau âtidak dapat dipotong.â Namun, kemudian, Plato dan Aristoteles merumuskan gagasan bahwa tidak mungkin ada partikel yang tidak dapat dibagi, dan pandangan âatomâ tentang materi memudar selama berabad-abad dimana filsafat Aristoteles mendominasi budaya barat. Gagasan tentang atom muncul kembali di Eropa selama abad ke-17. Sebagai seorang kimia belajar mengukur jumlah elemen yang bereaksi satu sama lain untuk membentuk zat baru. Teori ini dikemukakan oleh John Dalton pada abad ke-18, teori atom Dalton ini memberikan gambaran model atom seperti bola pejal atau model bola billiard Discover the world's research25+ million members160+ million publication billion citationsJoin for free TUGAS KE â 1 KIMIA DASARRANGKUMAN MATERI ATOM, ION, DAN MOLEKULKELOMPOK 1 KELAS C 1 Ahmad Dwi Pandu Ainul Azis 270110190011 Teori Atomik dan Materi2 Aliyuddin Jamil 270110190012 Penemuan Struktur Atomik3 Rifky Ahmad Raihan 270110190013 Teori Modern Mengenai Struktur Atom4 Muhamad Ichsan 270110190014 Berat Atom dan Hubungannya Pada Masing-Masing Atom5 Astrina Salsabila Khumaedi 270110190015 Tabel Periodik6 Qolbu Naufal Phasaby 270110190036 Molekul dan Senyawa Molekuler7 Jiya Ulhaq 270110190037 Ion dan Senyawa Ionik8 Andre Windo Sinaga 270110190038 Beberapa Senyawa Anorganik Sederhana9 Muhammad Afghan Kemal Lazuardi 270110190039 Penamaan Senyawa Anorganik10 Nizalia Azzahra Yoza 270110190040 Teori Modern Mengenai Struktur Atom11 Johanes Adrian Santoso 270110190061 Penemuan Struktur Atomik12 Hamzah Abdirrohman 270110190062 Teori Modern Mengenai Struktur Atom13 Farhan Adi Guna 270110190063 Berat Atom dan Hubungannya Pada Masing-Masing Atom14 Rayhan Aulia Zaenuddin 270110190064 Tabel Periodik15 Lizzy Evsa Audrey 270110190065 Molekul dan Senyawa MolekulerUNIVERSITAS PADJADJARANFAKULTAS TEKNIK GEOLOGI2019 A. TEORI ATOMIK DAN MATERISeorang filsuf terdahulu yang berasal dari Yunani Demokritus 460-370 SMmenyatakan bahwa semua materi terdiri dari partikel-partikel kecil yang tidak dapatdibagi lagi yang disebut sebagai atomos yang berarti âtidak dapat dibagiâ atau âtidakdapat dipotong.â Namun, kemudian, Plato dan Aristoteles merumuskan gagasanbahwa tidak mungkin ada partikel yang tidak dapat dibagi, dan pandangan âatomâtentang materi memudar selama berabad-abad dimana filsafat Aristotelesmendominasi budaya tentang atom muncul kembali di Eropa selama abad ke-17. Sebagaiseorang kimia belajar mengukur jumlah elemen yang bereaksi satu sama lain untukmembentuk zat baru. Teori ini dikemukakan oleh John Dalton pada abad ke-18, teoriatom Dalton ini memberikan gambaran model atom seperti bola pejal atau model bolabilliard. Teori Atom Menurut Beberapa Tokohï· Thomson 1897, Menurut model atom Thomson, elektron bermuatan negatiftersebar dalam bola bermuatan positif seperti model roti kismis, di manakismis-kismis adalah elektron-elektron, dan roti adalah bola bermuatan positif.ï·Rutherford 1911, di mana dalam atom yang sebagian besar merupakan ruangkosong terdapat inti yang padat pejal dan masif bermuatan positif yang disebutsebagai inti atom; dan elektron-elektron bermuatan negatif yang mengitari intiatom. Ia juga menemukan partikel positif yang disebut proton.ï·Bohr 1913, Pada tahun 1913, Niels Bohr mengajukan model atom untukmenjelaskan fenomena penampakan sinar dari unsur-unsur ketika dikenakanpada nyala api ataupun tegangan listrik tinggi. Oleh karena itu, model atomBohr disebut juga model tata suryaï·Mekanika kuantum 1924, pada tahun 1924, Louis de Broglie menyatakandualisme partikel gelombang semua materi dapat memiliki sifat sepertigelombang model atom mekanika kuantum disebut juga model awan PENEMUAN STRUKTUR ATOMIKPerkembangan struktur atom disumbangkan oleh banyak ilmuwan. Kronologidari struktur atom mengungkapkan penemuan partikel atom dan pengaturan mereka didalam atom. Atom adalah bahan dasar penyusun dari semua zat. Sebuah atom terdiridari tiga partikel â neutron tanpa muatan, proton bermuatan positif dan elektronbermuatan negatif. Jumlah proton yang terdapat dalam atom disebut nomor atom, sedangkan massa atom adalah jumlah proton ditambah rata-rata jumlah unsur yang berbeda yang ditemukan di alam berbeda dalam hal jumlah dariketiga partikel umum nomor atom digunakan untuk mendefinisikan sebuah unsur,misalnya, suatu unsur dengan nomor atom 8 adalah oksigen dan sebaliknya. Sebuahunsur memiliki sejumlah proton yang tetap, tetapi dapat memiliki jumlah neutronyang bervariasi. Atom dengan jumlah neutron yang berbeda disebut sebagai atom itu ada sejak jaman Yunani. Hal itu disampaikan olehDemocritus 460 SM sebagai Atoma, bahasa Yunani yang berarti tak dapat pujian sebenarnya untuk penemuan atom masuk ke John Dalton yangmengajukan teori atom dan menyarankan bahwa semua hal terdiri dari partikel padatbola yang disebut atom. Setelah penemuan atom, banyak perbaikan yang telah dibuattentang atom dan struktur Tabel Periodik MendeleevDmitri Mendeleev mengatur unsur dengan sifat yang mirip dalam tujuh juga mengusulkan hukum periodik, yang menyatakan bahwa sifat-sifat unsurberbeda berdasarkan berat Penemuan ElektronJoseph John Thompson mengklaim bahwa atom bisa mengeluarkan partikelbermuatan negatif kecil, yang ia disebut sebagai Inert 1904Abegg menyatakan bahwa stabilitas dan aktivitas kimia gas inert adalah karenakonfigurasi elektron mereka yang Inti AtomErnest Rutherford menyatakan bahwa inti atom adalah struktur yang sangat padat danbermuatan positif. Dia adalah yang pertama untuk mengasumsikan posisi elektron disekitar Muatan dalam IntiHGJ Moseley menemukan muatan positif inti atom. Menurut dia, jumlah atom suatuunsur sama dengan jumlah Isotop Aston menemukan keberadaan atom dengan jumlah neutron yang berbeda untukpertama kalinya dengan menggunakan spektrograf massa. Dia menyebut merekasebagai orbitalNiels Bohr menjelaskan struktur atom dan adanya orbit. Model atom terdiri dari kulitberturut-turut di mana elektron Sifat Dasar Dualitas AtomDe Broglie menemukan sifat ganda pada elektron. Dia mengusulkan bahwa elektrondapat berperilaku sebagai gelombang atau sebagai Formula AtomHeisenberg mulai membuat representasi atom dengan rumus. Dia mendirikan prinsipketidakpastian yang menyatakan bahwa posisi dan kecepatan partikel tidak dapatditentukan pada waktu yang Model AtomSchrodinger mengamati elektron sebagai awan yang kontinu. Dia memperkenalkangelombang mekanik dalam model Penemuan NeutronJames Chadwick menemukan neutron dengan menggunakan partikel alpha. Diamenyarankan bahwa massa neutron adalah mirip dengan TEORI MODERN MENGENAI STRUKTUR ATOMAtom adalah suatu bagian terkecil dari suatu unsur dan setiap apa-apa yangada di muka bumi ini tersusun oleh atom. Oleh sebab itu kita harus mengetahuistruktur-struktur dari penyusun atom tersebut. Ada 3 penyusun atom yaitu proton,neutron, dan juga elektron. Proton merupakan partikel penyusun inti atom yangbermuatan positif +. Selain proton, ada pula neutron yang memiliki muatan elektron tidak menempati inti atom melainkan membentuk orbitnyasendiri di sekitar atom. Dan elekton ini memiliki muatan negatif - Proton dan elektron memiliki gaya saling tarik menarik. Gaya tersebut disebutelectronic charge. Gaya ini berfungsi sebagai gaya yang menstabilkan atom. Nilaikuantitatif dari gaya ini adalah x 10-19C untuk elektron dan + x 10-19Cuntuk proton. Jari-jari atom adalah jarak dari inti atom ke orbital elektron terluaryang stabil dalam suatu atom dalam keadaan setimbang. Biasanya jarak itu diukur dalam satuan pikometer atau angstrom. Diameter inti atom berkisar antara 10-15hingga 10-14 ï·Bilangan Atom, Bilangan Massa, dan IsotopDi dalam unsur-unsur yang terdapat pada tabel periodik, setiap unsurnyaemiliki karakteristik yang berbeda. Salah satu karakteristik yang membedakantersebut ialah perbedaan jumlah proton yang terdapat pada suatu unsur. Jumlahproton yang terdapat di dalam suatu unsur biasanya dituliskan sebagai bilanganatom. Jumlah suatu elektron pada suatu unsur sama dengan jumlah protonnyasehingga penulisannya biasanya diwakili oleh proton. Sedangkan pada unsur yangsama, terdapat kemungkinan bahwa jumlah neutron yang dikandungnya berbeda dariunsur yang sama. Contoh, dalam suatu unsur karbon memiliki 6 proton dan 6neutron sehingga unsur tersebut ditulis sebagai 126C, sedangkan unsur karbonyangmemiliki 6 proton dan 8 neutron ditulis sebagai 146C atau juga disebut sebagaikarbon-14. Jumlah dari proton dan neutron ini biasanya dituliskan sebagai bilanganmassa yang mewakiliberat suatu unsur suatu unsur yang memiliki massa bilangan yangberbeda dengan yangseharusnya, unsur ini disebut sebagai isotop. Isotop ini masih memiliki sifat yangsama dan identik secara kimiawi dengan unsur normalnya. Juga pada isotop inibiasanya disebut dengan nama lain, contoh 136C akan disebut sebagai karbon-13,sedangkan 126C disebut sebagai karbon BERAT ATOM DAN HUBUNGANNYA PADA MASING-MASING ATOMPara ilmuwan pada abad kesembilan belas menyadari bahwa masing masingatom yang ada memiliki massa yang berbeda. Pada atom sendiri terdapat nomor atomyang menyatakan jumlah proton dalam suatu atom, sehingga setiap atom memilikinomor atom yang berbeda pula. Kemudian nomor massa, yang menyatakan jumlahpartikel yang terdapat dalam inti atom yaitu proton dan atom ada yang disebut dengan isotop, isobar, dan Isotop, adalah atom-atom dengan nomor atom yang sama tetapi dengan nomor massaberbeda. 2. Isobar, adalah atom-atom dengan nomor atom yang berbeda tetapi dengan nomormassa yang Isoton, adalah atom-atom dengan jumlah neutron yang sama tetapi dengan nomoratom besar unsur terjadi di alam sebagai campuran isotop. Kita bisamenentukan rata-rata massa suatu atom yang biasa disebut berat atom. Dapatditentukan Berat atom = â [ nomor massa isotop ] [ kelimpahanisotop ].massa atom relatif dapat diketahui salah satunya dengan cara melihat yang paling akurat untuk menentukan berat atom adalah dengan spektometerspektometer. Spektometer massa adalah komposisi unsur dari bahan yang dianalisasehingga diketahui beart atau bobot molekulnya. Proses ionisasi menghasilkanpartikel partikel bermuatan posif, dimana massa terdistribusi. Prinsip spektometermassa yang pertama ialah ionisasi, atom diionisasi dengan mengambil satu atau lebihelektron dari atom tersebut. Spektometer ialah sampel dimasukkan dalam spektometermassa dari atom tersebut supaya terbentuk ion positif. Yang kedua adalah percepatanIon-ion tersebut dipercepat supaya semuanya mempunyai energi kinetik yang ketiga ialah ion-ion tersebut dibelokkan dengan mengggunakan medanmagnet,pembelokan yang terjadi tergantung pada masssa ionnya. Besarnyapembelokkannya tergantung pada berat muatan positif TABEL PERIODIKSejarah terbentuknya tabel periodik memiliki beberapa perkembangan yangdari awal mula hanya terdiri dari 33 unsur sampai sekarang ke zaman yang sudahmodern. Ada beberapa teori yang terbentuk dari teori pertama hingga teori di zamanmodern ini. Berikut teori-teori tersebut 1. Teori LavoisierPada tahun 1789, Antonie Lavoiser mengelompokan 33 unsur kimia dibagi menjadi empat kelompok. Yaitu gas, tanah, logam dan nonlogam.ï·Kelemahan teori Lavoiser Pengelompokan masih terlalu umum ï·Kelebihan teori Lavoiser Sudah mengelompokan 33 unsur yang adaberdasarkan sifat kimia sehingga bisa di jadikan referensi bagi ilmuwan-ilmuwan Hukum Oktaf merupakan orang pertama yang mengelompokan unsur-unsurberdasarkan kenaikan massa atom relatif. Newlands mengumumkanpenemuannya yang disebut Hukum Oktaf. Ia menyatakan bahwa sifat-sifatunsur berubah secara pertama mirip dengan unsur kedelapan,unsurkedua mirip dengan unsur ke sembilan,dan seterusnya. Disebut hukum oktafkarena pola berulangnya sifat-sifat yang sama menyerupai oktaf dari teori ini adalah dalam kenyataanya masih di ketemukanbeberapa oktaf yang isinya lebih dari delapan unsur. Dan penggolongan ini tidakcocok untuk unsur yang massa atomnya sangat Sistem Periodik MendeleevPada tahun 1869 Dmitri Ivanovich Mendeleev mengamati 63 unsur yang sudahdikenalnya dan Ia menyimpulkan bahwa sifat-sifat unsur adalah fungsi periodikdari massa atom relatifnya. Artinya, jika suatu unsur-unsur disusun menurutkenaikan massa atom relatifnya, maka sifat tertentu akan berulang secaraperiodik. Mendeleev menempatkan unsur-unsur yang mempunyai kemiripansifat dalam satu jalur vertical yang disebut golongan. Lajur-lajur horizontal,yaitu lajur unsur unsur berdasarkan kenaikan massa atom relatifnya, disebutperiode. ï·Kelemahan masih terdapat unsur-unsur yang massanya lebih besarletaknya di depan unsur yang massanya lebih kecilï·Kelebihan peramalan unsur baru yakni meramalkan unsur beserta sifat-sifatnya. 4. Sistem Periodik Modern Henry G. MoseleyHenry Moseley pada tahun 1913 melakukan percobaan yakni pengukuranpanjang gelombang unsur menggunakan sinar X. Ia menyimpulkan bahwa sifatdasar atom bukan didasari oleh massa atom relative,melaikan berdasarkankenaikan jumlah proton. Hal tersebut dakibatkan oleh isotop atau unsur yangmemiliki massa atom yang berbeda hanya saja memiliki jumlah proton yangsama. Sistem periodik modern disusun berdasarkan kenikan massa atom dankemiripan antar unsur. Lajurâlajur horizontal disusun berdasarkan kenikannomor atom sedangkan jalur âjalur vertikan disusun berdasarkan kemiripansifat. 5. Sistem Periodik Lothar MeyerLothar Meyer ,engusulkan sistem periodik berdasarkan masa atom. Menurutmeyer, volume atom suatu unsur yang diplotkan dengan massa atom tersebutakan membentuk grafik yang berperiodik secara teratur. Dalam tabel periodikMeyer disusun berdasarkan kenaikan massa atom secara vertikal. Unsur âunsuryang sifatnya mirip ditempatkan secara horizontal.ï·Kelebihan -Lebih sederhana dan mudah di mengerti dibandingan dengan tabel periodik mengklasifikasikan elemen bukan dengan berat atom melaikan hanya valensi nya saja.ï·Kekurangan Tidak jauh berbeda dengan tabel periodick Mendeleev 6. Sistem Periodik Modern Bentuk sistem periodik modern adalah berupa tabel panjang yang dimodifikasidengan cara mengeluarkan dua deret unsur-unsur yang tergolong unsur-unsurtransisi dalam, yaitu unsur-unsur dimulai denga nomor atom 58 hingga 71 golongan lantanida dan nomor atom 90 samapai 103 golongan aktinida Dalam sistem periodik modern unsur-unsur disusun berdasarkan kenaikannomor atom bukan nomor massanya. Terdapat 7 periode dengan 18 1 dihuni 2 unsur ; periode 2 dan 3 dihuni 8 unsur ; periode 4 dan 5dihuni 18 unsur ; periode 6 dan 7 dihuni 32 unsur . Oleh karena telalu panjangmaka pada periode 6 dan 7 unsur dengan nomor atom 58-71 dan 90-103dikeluarkan dari tabel dan ditempatkan dibawah tabel. F. MOLEKUL DAN SENYAWA MOLEKULERMolekul adalah kumpulan dari dua atau lebih atom yang terikat tersebut dapat berikatan karena adanya ikatan kimia. Atom-atom dariunsur yang berbeda dapat berikatan satu sama lain untuk membentuk suatu senyawa. Berdasarkan jenis ikatannya, senyawa dibagi menjadi dua, yaitu senyawamolekuler/senyawa kovalen, dan senyawa ionik. Senyawa molekuler/senyawakovalen adalah senyawa yang terbentuk karena adanya ikatan kovalen. Ikatan kovalenadalah ikatan yang terjadi karena adanya pemakaian elektron secara bersama-samaoleh unsur-unsur yang berikatan. Sementara senyawa ionik adalah senyawa yangterbentuk karena adanya ikatan ionik. Ikatan ionik adalah ikatan yang terjadi karenaadanya serah-terima elektron antara unsur-unsur yang ION DAN SENYAWA IONIK Istilah Ion pertama kali dikemukakan oleh Michael Faraday pada tahun adalah atom yang memiliki muatan listrik. Sesuai dengan listrik yang memilikimuatan positif dan negatif begitu juga ion. Ion dibedakan menjadi dua macam yaituion bermuatan positif kation dan ion bermuatan negatif anion.Senyawa yang terbentuk dari muatan listrik masing masing ion pembentuknyadisebut dengan senyawa ionik. Secara umum senyawa ionik terbentuk dari atomlogam bermuatan positif dan atom non logam bermuatan negatif. Contoh senyawaionik yang sering ditemukan dalam kehidupan sehari hari ialah garam dapurNaCl.Garam dapur tersusun atas atom Na+ dan Cl-, dimana atom Na memiliki muatan positifsedangkan atom Cl memiliki muatan negatif. Senyawa ionik memiliki keunikantersendiri dimana ketika senyawa ionik dilarutkan ke dalam air maka senyawa ionikakan larut dan terpecah menjadi atom atom nya sendiri yang memiliki muatanberbeda, hal inilah yang menyebabkan air yang dilarutkan senyawa ionik kedalam nyaakan dapat menghantarkan PENAMAAN SENYAWA ANORGANIKPenamaan senyawa kimia dikenal dengan nama chemical senyawa kimia dibagi menjadi tiga pengelompokkan, yaitu senyawa ion,senyawa asam, dan senyawa molekul biner. a. Senyawa IonSenyawa ion terdiri dari kation dan anion, kation ditulis lebih dulu dan diikuti olehanion. 1. Kation yang terbentuk dari atom logam dan memiliki penyebutan yang samadengan nama logamnya, contoh Na ion natrium sedangkan jika logamâștersebut memiliki muatan, maka jumlah muatan positif ditulis dengan angkaromawi di dalam kurung, contoh Fe3+ ion besi III. Kation yang terbentukdari atom non-logam akan memiliki akhiran âium, contoh NH ammonium.ââș2. Anion terbentuk dari atom non-logam. Anion monoatomic akan memiliki akhiranâida, contoh H ion hidrida. Untuk beberapa anion poliatomik juga memilikiâ»akhiran âida, contoh OH ion hidroksida. Anion yang memiliki atom Oâ»disebut oxyanions dan akan memiliki akhiran âat atau âit. Akhiran âat digunakanpada kebanyakan anion, dan akhiran âit akan digunakan oleh anion dengan komposisi sama namun dengan atom O yang lebih sedikit satu atom, contoh NO nitrat dan NO nitrit. Kata depan digunakan jika dalam senyawa anionââ» ââ»terdapat unsur halogen, kata depan per- digunakan jika memiliki satu atom Olebih banyak daripada senyawa dengan akhiran âat, lalu kata depan hipo- akandigunakan jika memiliki satu atom O lebih sedikit daripada senyawa denganakhiran âit, contoh ClO ion perklorat, ClO ion klorat, ClO ion klorit,ââ» ââ» ââ»dan ClO ion hipoklorit. Anion yang terbentuk dari penambahan senyawa Hâ» âșakan memliki kata depan hidrogen- atau dihidrogen-, contoh HCO hidrogenââ»karbonat. Dalam metode penamaan yang lebih tua, kata depan hidrogen biasajuga diganti dengan kata depan bi-, maka HCO akan bernama ion Senyawa Asam Senyawa asam adalah senyawa yang mengeluarkan ion H saat larut di dalam air,âșdalam penamaan atom H ditulis di awal dan diikuti elemen lainnya. Cara penamaannya adalah dengan menambahkan kata depan hidro- dan mengganti akhiran âidamenjadi akhiran âat pada nama anion yang terkandung dalam senyawa asam, contoh Cl klorida maka menjadi HCl asam hidroklorat. Untuk penamaan asam yangâ»mengandung anion dengan akhiran âat, maka tinggal menambahkan kata asam padapenamaannya, contoh ClO perklorat menjadi HClO asam perklorat. ââ» âc. Senyawa Molekul BinerUntuk penamaan seyawa molekul biner, unsur yang terdapat di sebelah kiri tabel periodik unsur dekat dengan unsur logam akan ditulis diawal, kecuali jika senyawa tersebut mengandung oksigen, klor, brom, atau iodin seluruh unsur halogen kecuali fluor, karena oksigen akan ditulis di akhir. Jika senyawa tersebbut terbuat dari unsur dalam golongan yang sama, maka unsur yang lebih bawah akan ditulis lebih dahulu. Nama unsur yang terakhir, diberi akhiran âida. Kata depan berbahasa yunani menunjukkan jumlah unsur yang terdapat dalam senyawa tersebut, seperti mono satu, di dua, tri tiga, dan seterusnya. Contoh nya adalah Cl O diklormonoksida,âN O dinitrogentetroksida, dan lain âI. BEBERAPA SENYAWA ANORGANIK SEDERHANA1. Asam Asam merupakan suatu zat yang dapat memberi proton ion H+ kepada zat yang lain yang disebut basa, atau dapat menerima pasangan elektron bebas dari suatu basa. Asam dibagi 2 yaitu1. Asam yang tidak mengandung oksigen2. Asam yang mengandung oksigenContoh dari asama. HCLManfaat dapat membantu untuk mengancurkan bahan makanan yang masuk ke dalam HCL pekat dapat dapat membentuk kabut asam yang dapat bersifat korosif bagi jaringan b. H2SO4Manfaat sering digunakan pada praktikum biologi dan kimia, pemrosesan bijihmineral, dan pengilangan dapat menyebabkan luka BasaBasa merupakan senyawa yang dapat menghasilkan ion logam/gugus lain yangbermuatan positif serta gugus hidroksilOH- yang bermuatan dari basaa. NH3Manfaat digunakan untuk pembuatan obat-obatan, dapat digunakan untuk membersihkan berbagai perkakas rumah tangga, digunakan sebagai campuran pembuatan pupuk untuk penyedia unsur nitrogen bagi dapat menyebabkan kerusakan paru-paru dan bahkan kematian jika konsentrasinya CaOH2Manfaat salah satu bahan pembuatan limbah, pengelolaan pada tanah yang memilki keadaan cukup menyebabkan pengapauran dalam darah dan usus. 3. GaramGaram terbentuk dari asam bila semua atom H diganti dengan logam. Terbentuk dari basa bila semua gugus OH dganti dengan sisa a. NaClManfaat dapat digunakan untuk jalur infusKerugiaan dapat menyebabkan tekanan darah tinggi, stroke jika terlalu banyak CaCl2Manfaat pelebur es di jalan raya pada musim dingin, pengenyal dan menimbulkan kerak pada pipa air, ketel dan pipa radiator sehingga menyumbat PUSTAKA Brown. Bursten Murphy dan Woodward Stoltzfus . 2017 . Chemistry the Central Science 14 th Edition . New York . Pearson. Ahmad Dwi Pandu Ainul Azis 270110190011 2 Aliyuddin Jamil 270110190012 Rifky Ahmad Raihan 270110190013 Muhamad Ichsan 270110190014 Astrina Salsabila Khumaedi 270110190015 Qolbu Naufal Phasaby 270110190036 Jiya Ulhaq 270110190037 Andre Windo Sinaga 270110190038 Muhammad Afghan Kemal Lazuardi 270110190039 Nizalia Azzahra Yoza 270110190040 Johanes Adrian Santoso 270110190061 Hamzah Abdirrohman 270110190062 Farhan Adi Guna 270110190063 Rayhan Aulia Zaenuddin 270110190064 Lizzy Evsa Audrey 270110190065 Jari-jari atom emas Au adalah 1,35 Aa. jarak 1 Ă
= 1x10-10 = 0,1 nm = 100 pm = 10-8cm1,35 Ă
= 0,135 nm, dan 1,35 Ă
= 135 pmb. berapa banyak atom emas harus dilapisi hingga rentang 1,0 mm ?jarak 1 Ă
= 10-7mm maka butuh 107atomc. volume bola = 4/3Ïr3 = 4/3 x 3,14 1,35 x 10-83 = x10-24 cm3Exercise pertanyaan-pertanyaan berikuta. apa yang menjadi partikel sub-atomik utama yang dibuat naik atom ? proton, neutron, biaya relativedalam kelipatan muatan elektronik dari masingâmasing partikel ? 1836 elektron = proton dan 1829 elektron = neutronc. yang paling masif ? neutrond. yang paling tidak masif ? electronExercise atom 10B, Buron memiliki nomor atom 5a. banyak proton, neutron, electron ? electron=proton=nomor atom=5, neutron=nomor ditambah 1 proton maka akan menjadi Carbon C 11C nomor atom 5c. jika ditambah 1 neutron maka tetap, 10B no. atom 5â11B no. atom 5d. apakah salah satu dari atom yang diperoleh di jawaban b dan c isotope 10B, kalau begitu yang mana ? iya, yaitu bagian C, 11B no. atom 5Exercise a Define atomic number and mass number. b Which of these can vary without changing the identity of the element?Jawab a Nomor atom menunjukkan jumlah muatan positif dalam inti atom jumlah protonb Nomor massa jumlah total proton dan neutron nucleon di dalam inti atom yang menentukan massa atomic dari atomExercise many protons, neutrons, and electrons are in the following atoms? a 40Ar, b 65Zn, c 70Ga, d 80Br, e 184W, f a 40Ar Proton = 18 Elektron = 18 Neutron = 40-18 = 22b 65Zn Proton = 30 Elektron = 30 Neutron = 65-30 = 35c 70Ga Proton = 31 Elektron = 31 Neutron = 70-31 = 39d 80Br Proton = 35 Elektron = 35 Neutron = 80-35 = 45e 184W Proton = 74 Elektron = 74 Neutron = 184-74 = 110f 243Am Proton = 95 Neutron = 95 Elektron = 243-95 = 148 Exercise in the gaps in the following table, assuming each column represents a neutral 79Br Protons 25 82Neutrons 30 64 Electrons 48 86 Mass No. 222 207Jawab Symbol 79Br 55Mn 112Cd 222Rn 207PbProtons 35 25 48 86 82Neutrons 44 30 64 136 125Electrons 35 25 48 86 82Mass No. 79 55 112 222 207Exercise Exercise Terdapat duo isotop yang terbentuk secara alami 63CU massa atom = 62,9296 amu dan kelimpahan 69,17 % amu , dan 65CU Massa atom 64,9278 amu dan kelimpahan 30,83%.Hitung berat atom massa atom rata rata dari 69,17 % = 62,9296 dan 30,83 % = 0,3083. MakaBerat atom 0,6917 92,92960 amu + 0,30389 64,9278 amu = 43,55 amu + 20,23 amu = 63,55 amuExercise a Tabung sinar katoda Thompson dan massa spektrometer keduanya melibatkan penggunaan listrik atau medan magnet untuk membelokkan partikel bermuatan. Apakah partikel bermuatan yang terlibat dalam masing-masing percobaan ini? Pada tabung sinar katoda Thompson, partikel bermuatan negatif berarti elektron sementara dalam spektrometer massa digunakan partikel bermuatan positif. Partikel bermuatan positif ini adalah kation senyawa yang diamati b Apa label pada sumbu spektrum massa suatu atom? Sumbu y ialah kelimpahan relatif dansumbu x ialah rasio massa. c Untuk mengukur spektrum massa suatu atom, atom harus terlebih dahulu kehilangan satuatau lebih elektron. Yang anda harapkan lebih banyak dibelokkan dengan pengaturan yang sama dari medan listrik ion cl+ atau ion cl 2+? Ion cl + karena memiliki muatan atau ion yanglebih ringan sehingga ringan dibelokkan . Magnesium yang terjadi secara alami memiliki beberapa isotop KELIMPAHAN MASSA ATOM24Mg 78,99 23,98504 25Mg 10,00 24,9858426Mg 11,01 25,98259a Berapakah massa atom rata-rata?b Buatlah sketsa spektrum massa?a Berat atom = 0,789923,98504 amu + 0,124,98584 amu + 0,110125,98259 amu = 18,945783 amu + 2,498584 amu + 2,8606832 amu = 24,31 amub Exercise Tulis simbol kimia, cari di tabel periodik, berikan nomor atomnya, dan tentukan apakah itulogam, metaloid, atau bukan logam a kromium b helium c fosfor d seng e magnesium f bromin g arsenik. Jawab Kromium Simbol kimia CrNomor atom 24Termasuk logam HeliumSimbol kimia HeNomor atom 2Termasuk non logam Fosfor Simbol kimia PNomor atom 15Termasuk non logam Seng Simbol kimia ZnNomor atom 30Termasuk logam Magnesium Simbol kimia MgNomor atom 12Termasuk Logam Bromin Simbol kimia BrNomor atom 35Termasuk Non logam Arsenik Simbol Kimia AsNomor atom 33Termasuk Metaloid Exercise simbol kimianya, tentukan nama grup yang menjadi anggotanya Tabel dan menunjukkan apakah itu logam, metaloid, atau bukan logam a potassium b yodium c magnesium d argon e Potassium Simbol kimia KTermasuk golongan IA logam alkali Termasuk Logam YodiumSimbol Kimia ITermasuk golongan VIIA Halogen Termasuk Non logam Magnesium Simbol kimia MgTermasuk golongan IIA Alkali tanah Termasuk Logam Argon Simbol kimia ArTermasuk golongan VIIIA Gas mulia Termasuk Non logam Belerang Simbol Kimia STermasuk VI A Kalkogen Termasuk Non logam Exercise structural formulas of the compounds n-butane and isobutane are shown below. aDetermine the molecular formula of each. b Determine the empirical formula of each. cWhich formulasâempirical, molecular, or structuralâallow you determine these aredifferent compounds?a Rumus molekul n-butana = C4H10 Rumus molekul isobutana = C4H10 b Rumus empiris n-butana = C2H5 Rumus empiris isobutana = C2H5c Kita akan tahu perbedaan antara n-butana dan isobutana dari rumus strukturnya, karena bentuk struktur kedua senyawa tersebut berbedaExercise are the molecular and empirical formulas for each of the following compounds? a Rumus molekul N2H4 Rumus empiris NH2 b Rumus molekul N2H2 Rumus empiris NH c Rumus molekul NH3 Rumus empiris NH3Exercise Write the empirical formula corresponding to each of the following molecular formulas a Al2Br6 b C8H10c C4H8O2 P4O10 e C6H4Cl2 f B3N3H6Answera. AlBr3b. C4H5c. C2H4Od. P2O5e. C3H2Clf. BNH2Exercise How many hydrogen atoms are in each of the following a C2H5OH b CaC2H5COO2c NH43PO4Answera. 6b. 10c. 12Exercise Write the molecular and structural formulas for the compounds represented by the followingmolecular modelsAnswer a. Molecular formula C2H6O, Structural formula CH3OCH3b. Molecular formula C2H6O, Structural formula C2H5OHc. Molecular formula CH4O, Structural formula CH3OHMolecular formula PF3, Structural formula PF3Exercise Exercise Using the periodic table to guide you, predict the chemical formula and name of the compound formed by the following elements a. Ga and F = GaF2b. Li and H = LiHc. Al and I = AlI3d. K and S = K2SExercise Tentukan nama â nama senyawa ion yang terbentuk dari a Ca2 dan Brâș â»b K dan COâș â2 â»c Al3 dan CH COOH âș â â»d NH dan SOââș â2 â» e Mg2 dan POâș â3â»Jawaban a Ca2 dan Brâș â» = CaBrâ = Kalsium Bromidab K dan COâș â2â»= K CO â â = Kalsium Karbonatc Al3 dan CH COOH âș â â» = CH COOH Al = Alumunium Asetatâ âd NH dan SOââș â2 â» = NH SO â â â = Amonium Sulfate Mg2 dan POâș â3 â»= Mg PO â â â = Magnesium FosfatExercise Lengkapi tabel ini dengan mengisi formula senyawa ion dengan pasangan kation dan anionIon KâșNHââș Mg2âșFe3+Clâ»KCl NH ClâMgClâFeClâOHâ»KOH NH OHâMgOHâFeOHâCOâ2â»K COâ â NH COâ â â MgCOâFe CO â â âPOâ3â»K POâ â NH POâ â â Mg PO â â â FePOâ Exercise Predict whether each of the following compounds is molecular or ionic a. B2H6 = Molecularb. CH3OH = Molecularc. LiNO3 = Ionicd. Sc2O3 = Ionice. CsBr = Ionicf. NOCl = Molecularg. NF3 = Molecularh. Ag2SO4 = IonicExercise the following ionic compounds a Li2O, b FeCl3, c NaClO, d CaSO3, eCuOH2, f FeNO32, g CaCH3COO2, h Cr2CO33, i K2CrO4, j NH4 a Li2O = Lithium oksidab FeCl3 = BesiIII kloridac NaClO = Natrium hipokloritd CaSO3 = Kalsium sulfite e CuOH2 = TembagaII hidroksidaf FeNO32 = Besill nitratg CaCH3COO2 = kalsium asetath Cr2CO33 = KromIII karbonati K2CrO4 = Kalium kromatj NH42SO4 = ammonia sulfatExercise the chemical formulas for the following compounds a aluminum hydroxide, bpotassium sulfate, c copperI oxide, d zinc nitrate, e mercuryII bromide, f ironIIIcarbonate, g sodium a Alumunium hidroksida = AlOH3b Kalium sulfat = K2SO4c Tembaga I oksida = Cu2Od Zinc nitrat = ZnNO â âe Merkuri II bromida = HgBr2f Besi III karbonat = FeCO33g Natrium hipobromit = NaBrOExercise nama larutan asam atau nama rumus berdasarkan IUPAC !Jawab a HBrO3 = Asam bromatb HBr = Asam hidrobromatc H3PO4 = Asam fosfatd Hyphochlorous acid = HClOe Iodic acid = HIO3f Sulfurous acid = H2SO3Exercise nama larutan atau nama rumus berdasarkan IUPAC ! Jawab a SF6 = Sulfur heksafluoridab IF5 = Iodin pentafluoridac XeO3 = Xenon trioksidad Dinitrogen tetroxide = N2O4e Hydrogen cyanide = HCNf Tetraphosphorus hexasulfide = P4S6Exercise rumus kimia untuk setiap zat yang disebutkan di deskripsi kata berikut gunakan bagiandepan di dalam tutup untuk menemukan simbol untuk elemen yang tidak Anda ketahui.a. Seng karbonat dapat dipanaskan untuk membentuk seng oksida dan karbon dioksidaZnCO3 + O2ï ZnO + CO2b. Pada perawatan dengan asam fluorida, silikon dioksida membentuk silikontetrafluorida dan + 4HF ï SiF4 + 2H2Oc. Sulfur dioksida bereaksi dengan air untuk membentuk asam + H2O ï H2SO3d. Zat fosfor trihydride, biasa disebut fosfin, adalah gas Asam perklorat bereaksi dengan kadmium untuk membentuk kadmium II + Cd ï Cd2HClO4f. Vanadium III bromide adalah padatan A Apa itu hidrokarbon? B Pentana adalah alkana dengan rantai lima atom karbon. Tulisformula struktural untuk senyawa ini dan tentukan rumus molekul dan Hidrokarbon adalah senyawa kimia yang terdiri atas unsur karbon C dan unsurhidrogen H yang berikatan satu sama Alkana, rumus empiris CnH2n+2Pentana C5H12 Exercise ResearchGate has not been able to resolve any citations for this has not been able to resolve any references for this publication.
A= 50 + 62 = 112 03) (Covest-2002) Istopos radiativos de iodo so utilizados no diagnstico e tratamento de problemas da tireide, e so, em geral, ministrados na forma de sais de iodeto. O nmero de prtons, nutrons e eltrons no istopo 131 131 do iodeto 53 I so, respectivamente: a) 53, 78 e 52. b) 53, 78 e 54. c) 53, 131 e 53. d) 131, 53 e 131.
Last updated Save as PDF Page ID369176 Learning Objectives Describe the locations, charges, and masses of the three main subatomic particles. Determine the number of protons and electrons in an atom. Write and interpret symbols that depict the atomic number, mass number, and charge of an atom or ion. Define the atomic mass unit and average atomic mass Dalton's Atomic Theory explained a lot about matter, chemicals, and chemical reactions. Nevertheless, it was not entirely accurate, because contrary to what Dalton believed, atoms can, in fact, be broken apart into smaller subunits or subatomic particles. We have been talking about the electron in great detail, but there are two other particles of interest to us protons and neutrons. We already learned that J. J. Thomson discovered a negatively charged particle, called the electron. Rutherford proposed that these electrons orbit a positive nucleus. In subsequent experiments, he found that there is a smaller positively charged particle in the nucleus, called a proton. There is also a third subatomic particle, known as a neutron. Electrons Electrons are one of three main types of particles that make up atoms. Unlike protons and neutrons, which consist of smaller, simpler particles, electrons are fundamental particles that do not consist of smaller particles. They are a type of fundamental particle called leptons. All leptons have an electric charge of \-1\ or \0\. Electrons are extremely small. The mass of an electron is only about 1/2000 the mass of a proton or neutron, so electrons contribute virtually nothing to the total mass of an atom. Electrons have an electric charge of \-1\, which is equal but opposite to the charge of a proton, which is \+1\. All atoms have the same number of electrons as protons, so the positive and negative charges "cancel out", making atoms electrically neutral. Unlike protons and neutrons, which are located inside the nucleus at the center of the atom, electrons are found outside the nucleus. Because opposite electric charges attract one another, negative electrons are attracted to the positive nucleus. This force of attraction keeps electrons constantly moving through the otherwise empty space around the nucleus. The figure below is a common way to represent the structure of an atom. It shows the electron as a particle orbiting the nucleus, similar to the way that planets orbit the sun. However, this is an incorrect perspective, as quantum mechanics demonstrates that electrons are more complicated. Figure \\PageIndex{1}\ Electrons are much smaller than protons or neutrons. If an electron was the mass of a penny, a proton or a neutron would have the mass of a large bowling ball! Protons A proton is one of three main particles that make up the atom. Protons are found in the nucleus of the atom. This is a tiny, dense region at the center of the atom. Protons have a positive electrical charge of one \\left +1 \right\ and a mass of 1 atomic mass unit \\left \text{amu} \right\, which is about \ \times 10^{-27}\ kilograms. Together with neutrons, they make up virtually all of the mass of an atom. Neutrons Atoms of all elementsâexcept for most atoms of hydrogenâhave neutrons in their nucleus. Unlike protons and electrons, which are electrically charged, neutrons have no chargeâthey are electrically neutral. That's why the neutrons in the diagram above are labeled \n^0\. The zero stands for "zero charge". The mass of a neutron is slightly greater than the mass of a proton, which is 1 atomic mass unit \\left \text{amu} \right\. An atomic mass unit equals about \ \times 10^{-27}\ kilograms. A neutron also has about the same diameter as a proton, or \ \times 10^{-15}\ meters. As you might have already guessed from its name, the neutron is neutral. In other words, it has no charge whatsoever and is therefore neither attracted to nor repelled from other objects. Neutrons are in every atom with one exception, and they are bound together with other neutrons and protons in the atomic nucleus. Before we move on, we must discuss how the different types of subatomic particles interact with each other. When it comes to neutrons, the answer is obvious. Since neutrons are neither attracted to nor repelled from objects, they don't really interact with protons or electrons beyond being bound into the nucleus with the protons. Even though electrons, protons, and neutrons are all types of subatomic particles, they are not all the same size. When you compare the masses of electrons, protons, and neutrons, what you find is that electrons have an extremely small mass, compared to either protons or neutrons. On the other hand, the masses of protons and neutrons are fairly similar, although technically, the mass of a neutron is slightly larger than the mass of a proton. Because protons and neutrons are so much more massive than electrons, almost all of the mass of any atom comes from the nucleus, which contains all of the neutrons and protons. Table \\PageIndex{1}\ Properties of Subatomic Particles Particle Symbol Mass amu Relative Mass proton = 1 Relative Charge Location proton p+ 1 1 +1 inside the nucleus electron eâ Ă 10â4 â1 outside the nucleus neutron n0 1 1 0 inside the nucleus Table \\PageIndex{1}\ gives the properties and locations of electrons, protons, and neutrons. The third column shows the masses of the three subatomic particles in "atomic mass units." An atomic mass unit \\text{amu}\ is defined as one-twelfth of the mass of a carbon-12 atom. Atomic mass units \\text{amu}\ are useful, because, as you can see, the mass of a proton and the mass of a neutron are almost exactly \1\ in this unit system. Negative and positive charges of equal magnitude cancel each other out. This means that the negative charge on an electron perfectly balances the positive charge on the proton. In other words, a neutral atom must have exactly one electron for every proton. If a neutral atom has 1 proton, it must have 1 electron. If a neutral atom has 2 protons, it must have 2 electrons. If a neutral atom has 10 protons, it must have 10 electrons. You get the idea. In order to be neutral, an atom must have the same number of electrons and protons. Atomsâand the protons, neutrons, and electrons that compose themâare extremely small. For example, a carbon atom weighs less than 2 \\times\ 10â23 g, and an electron has a charge of less than 2 \\times\ 10â19 C coulomb. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit amu and the fundamental unit of charge e. The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are assigned masses of exactly 12 amu. This isotope is known as âcarbon-12â as will be discussed later in this module. Thus, one amu is exactly \1/12\ of the mass of one carbon-12 atom 1 amu = \\times\ 10â24 g. The Dalton Da and the unified atomic mass unit u are alternative units that are equivalent to the amu. Atomic Number The number of protons in the nucleus of an atom is its atomic number \Z\. This is the defining trait of an element Its value determines the identity of the atom. For example, any atom that contains six protons is the element carbon and has the atomic number 6, regardless of how many neutrons or electrons it may have. A neutral atom must contain the same number of positive and negative charges, so the number of protons equals the number of electrons. Therefore, the atomic number also indicates the number of electrons in an atom. The total number of protons and neutrons in an atom is called its mass number A. The number of neutrons is therefore the difference between the mass number and the atomic number A â Z = number of neutrons. \[\begin{align*} \ce{atomic\ number\Z\ &= \number\ of\ protons\\ mass\ number\A\ &= \number\ of\ protons + number\ of\ neutrons\\ A-Z\ &= \number\ of\ neutrons} \end{align*} \nonumber \] Atoms are electrically neutral if they contain the same number of positively charged protons and negatively charged electrons. When the numbers of these subatomic particles are not equal, the atom is electrically charged and is called an ion. The charge of an atom is defined as follows Atomic charge = number of protons â number of electrons As will be discussed in more detail later in this chapter, atoms and molecules typically acquire charge by gaining or losing electrons. An atom that gains one or more electrons will exhibit a negative charge and is called an anion. Positively charged atoms called cations are formed when an atom loses one or more electrons. For example, a neutral sodium atom Z = 11 has 11 electrons. If this atom loses one electron, it will become a cation with a 1+ charge 11 â 10 = 1+. A neutral oxygen atom Z = 8 has eight electrons, and if it gains two electrons it will become an anion with a 2â charge 8 â 10 = 2â. Example \\PageIndex{1}\ Composition of an Atom Iodine is an essential trace element in our diet; it is needed to produce thyroid hormone. Insufficient iodine in the diet can lead to the development of a goiter, an enlargement of the thyroid gland Figure \\PageIndex{2}\. Figure \\PageIndex{2}\ a Insufficient iodine in the diet can cause an enlargement of the thyroid gland called a goiter. b The addition of small amounts of iodine to salt, which prevents the formation of goiters, has helped eliminate this concern in the US where salt consumption is high. credit a modification of work by âAlmaziâ/Wikimedia Commons; credit b modification of work by Mike Mozart The addition of small amounts of iodine to table salt iodized salt has essentially eliminated this health concern in the United States, but as much as 40% of the worldâs population is still at risk of iodine deficiency. The iodine atoms are added as anions, and each has a 1â charge and a mass number of 127. Determine the numbers of protons, neutrons, and electrons in one of these iodine anions. Solution The atomic number of iodine 53 tells us that a neutral iodine atom contains 53 protons in its nucleus and 53 electrons outside its nucleus. Because the sum of the numbers of protons and neutrons equals the mass number, 127, the number of neutrons is 74 127 â 53 = 74. Since the iodine is added as a 1â anion, the number of electrons is 54 [53 â 1â = 54]. Exercise \\PageIndex{1}\ An ion of platinum has a mass number of 195 and contains 74 electrons. How many protons and neutrons does it contain, and what is its charge? Answer 78 protons; 117 neutrons; charge is 4+ Chemical Symbols A chemical symbol is an abbreviation that we use to indicate an element or an atom of an element. For example, the symbol for mercury is Hg Figure \\PageIndex{3}\. We use the same symbol to indicate one atom of mercury microscopic domain or to label a container of many atoms of the element mercury macroscopic domain. Figure \\PageIndex{3}\ The symbol Hg represents the element mercury regardless of the amount; it could represent one atom of mercury or a large amount of mercury. from Wikipedia user Materialscientist. The symbols for several common elements and their atoms are listed in Table \\PageIndex{2}\. Some symbols are derived from the common name of the element; others are abbreviations of the name in another language. Symbols have one or two letters, for example, H for hydrogen and Cl for chlorine. To avoid confusion with other notations, only the first letter of a symbol is capitalized. For example, Co is the symbol for the element cobalt, but CO is the notation for the compound carbon monoxide, which contains atoms of the elements carbon C and oxygen O. All known elements and their symbols are in the periodic table. Table \\PageIndex{2}\ Some Common Elements and Their Symbols Element Symbol Element Symbol aluminum Al iron Fe from ferrum bromine Br lead Pb from plumbum calcium Ca magnesium Mg carbon C mercury Hg from hydrargyrum chlorine Cl nitrogen N chromium Cr oxygen O cobalt Co potassium K from kalium copper Cu from cuprum silicon Si fluorine F silver Ag from argentum gold Au from aurum sodium Na from natrium helium He sulfur S hydrogen H tin Sn from stannum iodine I zinc Zn Traditionally, the discoverer or discoverers of a new element names the element. However, until the name is recognized by the International Union of Pure and Applied Chemistry IUPAC, the recommended name of the new element is based on the Latin words for its atomic number. For example, element 106 was called unnilhexium Unh, element 107 was called unnilseptium Uns, and element 108 was called unniloctium Uno for several years. These elements are now named after scientists or locations; for example, element 106 is now known as seaborgium Sg in honor of Glenn Seaborg, a Nobel Prize winner who was active in the discovery of several heavy elements. Isotopes The symbol for a specific isotope of any element is written by placing the mass number as a superscript to the left of the element symbol Figure \\PageIndex{4}\. The atomic number is sometimes written as a subscript preceding the symbol, but since this number defines the elementâs identity, as does its symbol, it is often omitted. For example, magnesium exists as a mixture of three isotopes, each with an atomic number of 12 and with mass numbers of 24, 25, and 26, respectively. These isotopes can be identified as 24Mg, 25Mg, and 26Mg. These isotope symbols are read as âelement, mass numberâ and can be symbolized consistent with this reading. For instance, 24Mg is read as âmagnesium 24,â and can be written as âmagnesium-24â or âMg-24.â 25Mg is read as âmagnesium 25,â and can be written as âmagnesium-25â or âMg-25.â All magnesium atoms have 12 protons in their nucleus. They differ only because a 24Mg atom has 12 neutrons in its nucleus, a 25Mg atom has 13 neutrons, and a 26Mg has 14 neutrons. Figure \\PageIndex{4}\ The symbol for an atom indicates the element via its usual two-letter symbol, the mass number as a left superscript, the atomic number as a left subscript sometimes omitted, and the charge as a right superscript. Information about the naturally occurring isotopes of elements with atomic numbers 1 through 10 is given in Table \\PageIndex{2}\. Note that in addition to standard names and symbols, the isotopes of hydrogen are often referred to using common names and accompanying symbols. Hydrogen-2, symbolized 2H, is also called deuterium and sometimes symbolized D. Hydrogen-3, symbolized 3H, is also called tritium and sometimes symbolized T. Table \\PageIndex{2}\ Nuclear Compositions of Atoms of the Very Light Elements Element Symbol Atomic Number Number of Protons Number of Neutrons Mass amu % Natural Abundance hydrogen \\ce{^1_1H}\ protium 1 1 0 \\ce{^2_1H}\ deuterium 1 1 1 \\ce{^3_1H}\ tritium 1 1 2 â trace helium \\ce{^3_2He}\ 2 2 1 \\ce{^4_2He}\ 2 2 2 100 lithium \\ce{^6_3Li}\ 3 3 3 \\ce{^7_3Li}\ 3 3 4 beryllium \\ce{^9_4Be}\ 4 4 5 100 boron \\ce{^{10}_5B}\ 5 5 5 \\ce{^{11}_5B}\ 5 5 6 carbon \\ce{^{12}_6C}\ 6 6 6 \\ce{^{13}_6C}\ 6 6 7 \\ce{^{14}_6C}\ 6 6 8 â trace nitrogen \\ce{^{14}_7N}\ 7 7 7 \\ce{^{15}_7N}\ 7 7 8 oxygen \\ce{^{16}_8O}\ 8 8 8 \\ce{^{17}_8O}\ 8 8 9 \\ce{^{18}_8O}\ 8 8 10 fluorine \\ce{^{19}_9F}\ 9 9 10 100 neon \\ce{^{20}_{10}Ne}\ 10 10 10 \\ce{^{21}_{10}Ne}\ 10 10 11 \\ce{^{22}_{10}Ne}\ 10 10 12 Atomic Mass Because each proton and each neutron contribute approximately one amu to the mass of an atom, and each electron contributes far less, the atomic mass of a single atom is approximately equal to its mass number a whole number. However, the average masses of atoms of most elements are not whole numbers because most elements exist naturally as mixtures of two or more isotopes. The mass of an element shown in a periodic table or listed in a table of atomic masses is a weighted, average mass of all the isotopes present in a naturally occurring sample of that element. This is equal to the sum of each individual isotopeâs mass multiplied by its fractional abundance. \[\mathrm{average\ mass}=\sum_{i}\mathrm{fractional\ abundance\times isotopic\ mass}_i \nonumber \] For example, the element boron is composed of two isotopes About of all boron atoms are 10B with a mass of amu, and the remaining are 11B with a mass of amu. The average atomic mass for boron is calculated to be \[\begin{align*} \textrm{boron average mass} &=\mathrm{ amu+ amu}\\ &=\mathrm{ amu+ amu}\\ &=\mathrm{ amu} \end{align*} \nonumber \] It is important to understand that no single boron atom weighs exactly amu; amu is the average mass of all boron atoms, and individual boron atoms weigh either approximately 10 amu or 11 amu. Example \\PageIndex{2}\ Calculation of Average Atomic Mass A meteorite found in central Indiana contains traces of the noble gas neon picked up from the solar wind during the meteoriteâs trip through the solar system. Analysis of a sample of the gas showed that it consisted of 20Ne mass amu, 21Ne mass amu, and 22Ne mass amu. What is the average mass of the neon in the solar wind? Solution \[\begin{align*} \mathrm{average\ mass} &=\mathrm{ amu+ amu+ amu}\\ &=\mathrm{ &=\mathrm{ amu} \end{align*} \nonumber \] The average mass of a neon atom in the solar wind is amu. The average mass of a terrestrial neon atom is amu. This result demonstrates that we may find slight differences in the natural abundance of isotopes, depending on their origin. Exercise \\PageIndex{2}\ A sample of magnesium is found to contain of 24Mg atoms mass amu, of 25Mg atoms mass amu, and of 26Mg atoms mass amu. Calculate the average mass of a Mg atom. Answer amu We can also do variations of this type of calculation, as shown in the next example. Example \\PageIndex{3}\ Calculation of Percent Abundance Naturally occurring chlorine consists of 35Cl mass amu and 37Cl mass amu, with an average mass of amu. What is the percent composition of Cl in terms of these two isotopes? Solution The average mass of chlorine is the fraction that is 35Cl times the mass of 35Cl plus the fraction that is 37Cl times the mass of 37Cl. \[\mathrm{average\ mass=fraction\ of\ ^{35}Cl\times mass\ of\ ^{35}Cl+fraction\ of\ ^{37}Cl\times mass\ of\ ^{37}Cl} \nonumber \] If we let x represent the fraction that is 35Cl, then the fraction that is 37Cl is represented by â x. The fraction that is 35Cl + the fraction that is 37Cl must add up to 1, so the fraction of 37Cl must equal â the fraction of 35Cl. Substituting this into the average mass equation, we have \[\begin{align*} \mathrm{ amu} &=x\times \ce{amu}+[ \ce{amu}]\\ &= &= x&=\dfrac{ \end{align*} \nonumber \] So solving yields x = which means that â = Therefore, chlorine consists of 35Cl and 37Cl. Exercise \\PageIndex{3}\ Naturally occurring copper consists of 63Cu mass amu and 65Cu mass amu, with an average mass of amu. What is the percent composition of Cu in terms of these two isotopes? Answer Cu-63 and Cu-65 Figure \\PageIndex{5}\ Analysis of zirconium in a mass spectrometer produces a mass spectrum with peaks showing the different isotopes of Zr. The occurrence and natural abundances of isotopes can be experimentally determined using an instrument called a mass spectrometer. Mass spectrometry MS is widely used in chemistry, forensics, medicine, environmental science, and many other fields to analyze and help identify the substances in a sample of material. In a typical mass spectrometer Figure \\PageIndex{5}\, the sample is vaporized and exposed to a high-energy electron beam that causes the sampleâs atoms or molecules to become electrically charged, typically by losing one or more electrons. These cations then pass through a variable electric or magnetic field that deflects each cationâs path to an extent that depends on both its mass and charge similar to how the path of a large steel ball bearing rolling past a magnet is deflected to a lesser extent that that of a small steel BB. The ions are detected, and a plot of the relative number of ions generated versus their mass-to-charge ratios a mass spectrum is made. The height of each vertical feature or peak in a mass spectrum is proportional to the fraction of cations with the specified mass-to-charge ratio. Since its initial use during the development of modern atomic theory, MS has evolved to become a powerful tool for chemical analysis in a wide range of applications. Video \\PageIndex{1}\ Watch this video from the Royal Society for Chemistry for a brief description of the rudiments of mass spectrometry. Summary An atom consists of a small, positively charged nucleus surrounded by electrons. The nucleus contains protons and neutrons; its diameter is about 100,000 times smaller than that of the atom. The mass of one atom is usually expressed in atomic mass units amu, which is referred to as the atomic mass. An amu is defined as exactly \1/12\ of the mass of a carbon-12 atom and is equal to \\times\ 10â24 g. Protons are relatively heavy particles with a charge of 1+ and a mass of amu. Neutrons are relatively heavy particles with no charge and a mass of amu. Electrons are light particles with a charge of 1â and a mass of amu. The number of protons in the nucleus is called the atomic number Z and is the property that defines an atomâs elemental identity. The sum of the numbers of protons and neutrons in the nucleus is called the mass number and, expressed in amu, is approximately equal to the mass of the atom. An atom is neutral when it contains equal numbers of electrons and protons. Isotopes of an element are atoms with the same atomic number but different mass numbers; isotopes of an element, therefore, differ from each other only in the number of neutrons within the nucleus. When a naturally occurring element is composed of several isotopes, the atomic mass of the element represents the average of the masses of the isotopes involved. A chemical symbol identifies the atoms in a substance using symbols, which are one-, two-, or three-letter abbreviations for the atoms. Key Equations \\mathrm{average\ mass}=\sum_{i}\mathrm{fractional\ abundance \times isotopic\ mass}_i\ Glossary anion negatively charged atom or molecule contains more electrons than protons atomic mass average mass of atoms of an element, expressed in amu atomic mass unit amu also, unified atomic mass unit, u, or Dalton, Da unit of mass equal to \\dfrac{1}{12}\ of the mass of a 12C atom atomic number Z number of protons in the nucleus of an atom cation positively charged atom or molecule contains fewer electrons than protons chemical symbol one-, two-, or three-letter abbreviation used to represent an element or its atoms Dalton Da alternative unit equivalent to the atomic mass unit fundamental unit of charge also called the elementary charge equals the magnitude of the charge of an electron e with e = \\times\ 10â19 C ion electrically charged atom or molecule contains unequal numbers of protons and electrons mass number A sum of the numbers of neutrons and protons in the nucleus of an atom unified atomic mass unit u alternative unit equivalent to the atomic mass unit Jumlahelektron pada ion kalium adalah . A. 16 B. 17 C. 18 D. 19 E. 20 3. Lambang suatu unsur 18 X 40 dapat disimpulkan bahwa pada satu atom unsur X mempunyai . A. 18 neutron dan 18 proton B. 22 neutron dan 22 proton C. 40 proton dan 18 elektron D. 18 proton dan 22 neutron E. 18 neutron, 22 proton, dan 22 elektron 4. Kelemahan teori atomNĂȘutron n Ă© uma pequena partĂcula que constitui o nĂșcleo do ĂĄtomo. NĂŁo tem carga e Ă© formada por partĂculas ainda menores, as quais recebem o nome de quarks. O nĂȘutron, ou neutrĂŁo em portuguĂȘs europeu, Ă© formado por dois quarks down e um quark com os prĂłtons p+, que tĂȘm carga positiva, os nĂȘutrons formam o centro do ĂĄtomo, o seu nĂșcleo. Isso apenas nĂŁo acontece com o hidrogĂȘnio, cujo nĂșcleo Ă© formado por apenas um fato de formar o nĂșcleo do ĂĄtomo, nĂȘutrons e prĂłtons sĂŁo chamados de nĂșcleons. Ă a carga positiva de um e a carga neutra do outro que propiciam a estabilidade a divisĂŁo do nĂșcleo do ĂĄtomo gera instabilidade e faz com que ele parta-se em dois. Tem origem uma reação em cadeia chamada FissĂŁo Nuclear, processo que Ă© utilizado no funcionamento das bombas elĂ©trons e-, cujas cargas sĂŁo negativas, localizam-se na eletrosfera, no exterior do ĂĄtomo e tĂȘm uma massa quase Calcular?A soma de nĂȘutrons n e de prĂłtons p+, que Ă© bastante semelhante, resulta no nĂșmero da massa atĂŽmica A, ou sejaA = p+ + nDaĂ decorre que o nĂșmero da massa A menos o nĂșmero atĂŽmico Z equivale ao nĂșmero de nĂȘutrons presentes em um ĂĄtomo, o que significan = A - ZIsso porque o nĂșmero de prĂłtons determina o nĂșmero elementos que tĂȘm o mesmo nĂșmero de nĂȘutrons sĂŁo chamados de isĂłtonos. Os isĂłtonos tĂȘm nĂșmero de massa e nĂșmero atĂŽmico mais em IsĂłtopos, IsĂłbaros e podem se decompor em prĂłtons e em elĂ©trons. Isso decorre do decaimento Beta ÎČ, o que faz o nĂȘutron se desintegrar. A emissĂŁo de Beta reduz o nĂȘutron e dĂĄ origem a um do NĂȘutronO nĂȘutron foi descoberto em 1932. A existĂȘncia dessa partĂcula jĂĄ havia sido sugerida por Ernest Rutherford 1871-19374 na dĂ©cada de 20, mas foi o cientista inglĂȘs James Chadwick 1891-1974 que a comprovou quando estava estudando a seus conhecimentos com exercĂcios sobre ĂĄtomos.
ztcG. 432 268 447 175 464 418 71 465 109
proton 74 elektron 74 neutron 112
