{"id":898,"date":"2019-10-07T12:32:18","date_gmt":"2019-10-07T12:32:18","guid":{"rendered":"http:\/\/chemdictionary.org\/?p=898"},"modified":"2019-10-07T12:32:25","modified_gmt":"2019-10-07T12:32:25","slug":"atomic-structure","status":"publish","type":"post","link":"https:\/\/chemdictionary.org\/atomic-structure\/","title":{"rendered":"Atomic Structure"},"content":{"rendered":"\n<p><strong> <\/strong><\/p>\n\n\n\n<h2><strong>Definition <\/strong><\/h2>\n\n\n\n<p>According\nto Dalton\u2019s theory atom is smallest particle which could not be divided any\nfurther. Atom is the entity that take part in a chemical reaction. For example,\nHe and Ne, etc. have atoms, which exists independently. While atoms of\nhydrogen, nitrogen and oxygen do not exist independently. <\/p>\n\n\n\n<p>An atom is further composed of subatomic particles like electron, proton, neutron, hypron, neutrino, anti-neutrino etc. more than 100 such particles are exist in an atom. However, Electron, Proton and Neutron are regarded as fundamental particles. An atom is composed of two regions: the nucleus, the center of atom contain proton and neutron, and the outer portion of the atom holds electrons in its orbit around the nucleus [1].<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" width=\"309\" height=\"255\" src=\"https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/10\/image-8.png\" alt=\"\" class=\"wp-image-899\" srcset=\"https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/10\/image-8.png 309w, https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/10\/image-8-300x248.png 300w\" sizes=\"(max-width: 309px) 100vw, 309px\" \/><\/figure>\n\n\n\n<p><strong>Ion <\/strong><\/p>\n\n\n\n<p>Ions\nare those species which have a positive or a negative charge. <\/p>\n\n\n\n<p>Whenever\nan atom of an element loses one or more electrons, positive ions are formed. A\nsufficient amount of energy is required to a neutral atom to ionize it.<\/p>\n\n\n\n<p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A \u2192\nA<sup>+<\/sup> + e<sup>&#8211;<\/sup><\/p>\n\n\n\n<p>This\nA<sup>+<\/sup> is called a cation.<\/p>\n\n\n\n<p>A\ncation may carry +1, +2, +3, etc. charge or charges. Formation of positive ions\nis an endothermic process. The most common positive ions are formed by the\nmetal atoms are Na<sup>+<\/sup>, K<sup>+<\/sup>, Ca<sup>+<\/sup>, Mg<sup>+<\/sup>,\nAl<sup>+ <\/sup>etc.<\/p>\n\n\n\n<p>When\na neutral atom picks up one or more electrons, a negative ion is produced,\nwhich is called an anion.<\/p>\n\n\n\n<p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B + e<sup>&#8211;<\/sup> \u2192 &nbsp;&nbsp;B<sup>&#8211;<\/sup><\/p>\n\n\n\n<p>Energy\nis released when an electron is introduced into an isolated atom. This is an\nexothermic process. The most common negative ions are F<sup>&#8211;<\/sup>, Cl<sup>&#8211;<\/sup>,\nBr<sup>&#8211;<\/sup>, S<sup>2-<\/sup> etc.<\/p>\n\n\n\n<p><strong>Atomic Mass Unit<\/strong><\/p>\n\n\n\n<p>It\nis defined as a unit of mass which is used to express atomic weight, it is\nequal to 1\/12<sup>th<\/sup> of the mass of carbon-12.<\/p>\n\n\n\n<p><strong>Orbital<\/strong><\/p>\n\n\n\n<p>It\nis the region in the atom where an electron is likely to be found.<\/p>\n\n\n\n<p><strong>Subatomic Particles<\/strong><\/p>\n\n\n\n<p><strong>Proton:<\/strong><\/p>\n\n\n\n<p>Proton\nis subatomic particle present in the center of atom making up nucleus. It has\npositive charge. The number of proton in an element\u2019s nucleus is known as\natomic number. In 1886, German physicist, E. Goldstein discovered positive rays\nthrough discharge tube provided with a perforated cathode. He projected alpha\nparticles on gold foil so the positive alpha particles were deflected. He said\nthat protons exist in the nucleus and have positive charge.<\/p>\n\n\n\n<p><strong>Properties <\/strong><\/p>\n\n\n\n<ul><li>They\nare deflected by an electric as well as magnetic field showing that these are\npositively charged.<\/li><li>The\ne\/m value for positive rays is always smaller than that of electron and also\ndepend upon nature of gas used in the discharge tube.<\/li><li>These\nrays travel in the straight line in a direction opposite to the cathode rays\n(electron).<\/li><\/ul>\n\n\n\n<p><strong>Neutron<\/strong><\/p>\n\n\n\n<p>The\nneutron is also subatomic particle having no net electric charge. Neutron is\npresent in nucleus along with proton. It is almost similar in mass to a proton.\nChadwick discovered neutron in 1932. Neutron determine the isotope of an atom\nand sometime stability of an atom.<\/p>\n\n\n\n<p><strong>Properties <\/strong><\/p>\n\n\n\n<ul><li>Neutron\ndo not ionize gases.<\/li><li>When\nneutrons are used as projectiles, they can carry out the nuclear reactions.<\/li><li>Neutrons\nare extremely penetrating particles.<\/li><li>They\ncan expel high speed protons from water, paper and cellulose.<\/li><\/ul>\n\n\n\n<p><strong>Electron <\/strong><\/p>\n\n\n\n<p>An\nelectron is negatively charged subatomic particle. It is present outside of and\nsurrounding the nucleus. An electron has a small mass as compared to neutron or\nproton, it carries negative charge (1.602 X 10<sup>-19<\/sup> coulomb). Electron\nwas discovered in 1897 by J. J. Thomson. Electrons can abbreviated as e<sup>&#8211;<\/sup>.<\/p>\n\n\n\n<p><strong>Properties <\/strong><\/p>\n\n\n\n<ul><li>The\nelectron has an intrinsic angular momentum.<\/li><li>Electron\ncan ionize gases.<\/li><li>It\nhas no known substructure.<\/li><\/ul>\n\n\n\n<table class=\"wp-block-table\"><tbody><tr><td>\n  <strong>Particle<\/strong>\n  <\/td><td>\n  <strong>Charge\n  (Coulomb)<\/strong>\n  <\/td><td>\n  <strong>Relative\n  charge<\/strong>\n  <\/td><td>\n  <strong>Mass\n  (kg)<\/strong>\n  <\/td><td>\n  <strong>Mass\n  (amu)<\/strong>\n  <\/td><\/tr><tr><td>\n  Proton\n  <\/td><td>\n  +1.6022 x 10 <sup>-19<\/sup>\n  <\/td><td>\n  +1\n  <\/td><td>\n  1.6726 x 10 <sup>-27<\/sup>\n  <\/td><td>\n  1.0073\n  <\/td><\/tr><tr><td>\n  Neutron\n  <\/td><td>\n  0\n  <\/td><td>\n  0\n  <\/td><td>\n  1.6750 x 10 <sup>-27<\/sup>\n  <\/td><td>\n  1.0087\n  <\/td><\/tr><tr><td>\n  Electron\n  <\/td><td>\n  -1.6022 x 10 <sup>-19<\/sup>\n  <\/td><td>\n  -1\n  <\/td><td>\n  9.1095 x 10 <sup>-31<\/sup>\n  <\/td><td>\n  5.4858 x 10<sup>4<\/sup>\n  <\/td><\/tr><\/tbody><\/table>\n\n\n\n<p><strong>&nbsp;Other Basic Atomic Particles<\/strong><strong><\/strong><\/p>\n\n\n\n<p><strong>Alpha Particles<\/strong><\/p>\n\n\n\n<p>They\ncan be denoted by He<sup>2+<\/sup>, \u03b1<sup>2+<\/sup> or \u03b1. They are helium nuclei\nand consist of two protons and two neutrons. Alpha particles are produced by\nalpha decay of an atom through which they become a new element. This process\noccur in those elements which have large radioactive nuclei. They are not\nharmful. Alpha decay process can be easily stopped through a sheet of paper or\nby skin. This process is mostly used in artificial heart pacemakers and space\nprobes [4].<\/p>\n\n\n\n<p><strong>Beta Particles<\/strong><\/p>\n\n\n\n<p>They are known as free electrons or positrons, having high energy and high speed. They are released as a result of beta decay. Positrons have the same mass as electrons but are positively charged. They have 100 times more penetrating power than alpha particles. Their emission can be stopped by household items like wood, plate or sheet. Beta particles are used in radiation to treat cancer. <\/p>\n\n\n\n<p><strong>Beta<sup>&#8211;<\/sup> (\u03b2<sup>&#8211;<\/sup>)\nor Electron Emission<\/strong><\/p>\n\n\n\n<p>They\ncan be produced when many neutrons make the nucleus of an atom unstable.\nNeutrons are decay and produced protons, an electron and an anti-neutrino.\nProton stay remains in the nucleus and electron and anti-neutrino are released.\nThe electron is called beta particle.<\/p>\n\n\n\n<p><strong>Beta<sup>+<\/sup> (\u03b2<sup>+<\/sup>)\nor positron Emission<\/strong><\/p>\n\n\n\n<p>When\nexcess of proton make the nucleus of an atom unstable. During the process\nproton is converted into neutron, a positron and a neutrino. Neutron remain\nstay in the nucleus but the positron and the neutrino are released.<\/p>\n\n\n\n<p><strong>Atomic Number<\/strong><\/p>\n\n\n\n<p>The\nnumber of proton in the nucleus of each atom of an element. The letter \u2018\u2019Z\u2019\u2019\nrepresents the number. <\/p>\n\n\n\n<p>For\nexample: The atomic number of nitrogen is 7. This means that nitrogen has 7\nproton and 7 electron.<\/p>\n\n\n\n<p><strong>Mass number<\/strong><\/p>\n\n\n\n<p>It\nis total number of proton and neutron present in the nucleus of each atom of an\nelement.<\/p>\n\n\n\n<p>Mass\nnumber = No. of proton + no of neutrons<\/p>\n\n\n\n<p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; = atomic number \u2013 no of\nneutron <\/p>\n\n\n\n<p>For\nexample: the mass number of fluorine is 19 and atomic number is 9. Thus the\nnumber of neutron in an atom of fluorine is 19-9 =10.<\/p>\n\n\n\n<p><strong>Isotopes <\/strong><\/p>\n\n\n\n<p><strong>Definition <\/strong><\/p>\n\n\n\n<p>The\nelement which exist in different forms, having same atomic number but different\nmass number. The isotopes that cannot decay during a defined period are called\nstable isotopes and the isotopes that can decay during a defined period are\ncalled unstable or radioactive isotopes [2].<\/p>\n\n\n\n<p>For\nexample: <\/p>\n\n\n\n<ol><li><strong>Isotopes of Hydrogen<\/strong>: There are three isotopes: protium, deuterium and tritium. Each has 1 proton and 1 electron but the number of neutrons is different. Tritium is radioactive isotope of hydrogen.<\/li><\/ol>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" width=\"580\" height=\"321\" src=\"https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/10\/image-9.png\" alt=\"\" class=\"wp-image-900\" srcset=\"https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/10\/image-9.png 580w, https:\/\/chemdictionary.org\/wp-content\/uploads\/2019\/10\/image-9-300x166.png 300w\" sizes=\"(max-width: 580px) 100vw, 580px\" \/><\/figure>\n\n\n\n<ul><li><strong>Isotopes of Carbon<\/strong>:\nIt has two stable isotopes <sup>12<\/sup>C and <sup>13<\/sup>C and one\nradioactive isotope <sup>14<\/sup>C.<\/li><li><strong>Isotopes of Chlorine:<\/strong>&nbsp; There are two isotopes of chlorine <sup>35<\/sup>Cl\nand <sup>37<\/sup>Cl.<\/li><li><strong>Isotopes of Uranium<\/strong>:\nThere are three isotopes of uranium <sup>234<\/sup>U, <sup>235<\/sup>U and <sup>238<\/sup>U.<\/li><\/ul>\n\n\n\n<p><strong>Quantum Numbers<\/strong><\/p>\n\n\n\n<p>These\nare the parameters that describe the distribution of electrons: these are as\nfollows [3].<\/p>\n\n\n\n<ol><li><strong>Principal\nQuantum Number:<\/strong><\/li><\/ol>\n\n\n\n<p>They\nrepresents the main energy level or shells occupied by the electrons, the value\nof n represents the shell or energy level in which the electrons are revolves\naround the nucleus. Letter notations K, L, M, N, etc are also used to denote\nthe various shells. <\/p>\n\n\n\n<p>For\nexample, when n=1, it is called K shell, for n=2 it is called L shell and so\non.<\/p>\n\n\n\n<p>The\nvalue of n also determine the location of electron in an atom, i.e the distance\nof electron from the nucleus, greater the value of \u2018n\u2019 greater will be distance\nof electron from the nucleus. It is quantitative measure of the size of an\nelectronic shell. \u2018n\u2019 also provides us the energy of electron in a shell.<\/p>\n\n\n\n<ul><li><strong>Secondary\nQuantum Number:<\/strong><\/li><\/ul>\n\n\n\n<p>They\nrepresents the energy sublevels occupied by the electrons. The values (<em>l<\/em>) are:<\/p>\n\n\n\n<p><em>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; l<\/em>=\n0,1,2, 3,\u2026\u2026\u2026\u2026\u2026\u2026\u2026..(n-1) <\/p>\n\n\n\n<p>Its\nvalue depend upon n. These values represents different subshells, which are\ndesigned by small letters, s, p, d, f. They stand for sharp, principal,\ndiffused and fundamental, respectively. <\/p>\n\n\n\n<p>A\nsubshell may have different shapes depending upon the value of <em>l.<\/em> <\/p>\n\n\n\n<p><em>l<\/em>=0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; s- subshell&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; spherical<\/p>\n\n\n\n<p><em>l<\/em>=1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; p subshell&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; dumb-bell<\/p>\n\n\n\n<p><em>l<\/em>=2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; d=subshell&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;complicated shape<\/p>\n\n\n\n<ul><li><strong>Magnetic\nQuantum Number<\/strong><\/li><\/ul>\n\n\n\n<p>They\nrepresents the possible orientation in 3-D space of each type of orbital.<\/p>\n\n\n\n<p>Its\nvalues are m= 0, +1, +2, +3, \u2026\u2026\u2026\u2026\u2026\u2026\u2026..<\/p>\n\n\n\n<p>The\nvalue of \u2018m\u2019 depends upon value of \u2018l\u2019. (2<em>l<\/em>+1).<\/p>\n\n\n\n<ul><li><strong>Spin\nQuantum Number<\/strong><\/li><\/ul>\n\n\n\n<p>They\nrepresent that in the presence of magnetic field electron can have two possible\norientation. Only two electrons can occupy the same orbital. <\/p>\n\n\n\n<p><strong>Electronic distribution <\/strong><\/p>\n\n\n\n<p>An\norbital like s, p<sub>x<\/sub>, p<sub>y<\/sub>, p<sub>z <\/sub>and d<sub>xy<\/sub>\netc. can have at the two most two electrons.<\/p>\n\n\n\n<p>The\nmaximum number of electrons that can be accommodate in a shell is given by 2n<sup>2<\/sup>\nformula where n is principle quantum number and it cannot have zero value.\nFollowing are the rules that have been adopted to distribute the electrons in\nsubshells or orbitals.<\/p>\n\n\n\n<ol><li>Aufbau\nprinciple<\/li><li>Pauli\u2019s\nexclusion principle<\/li><li>Hund\u2019s\nrule<\/li><\/ol>\n\n\n\n<p>The\narrangement of subshells in ascending order of their energy may be as follows:\n1s,2s,2p, 3s,3p,4s,3d,4p,5s,4d,5p.6s,4f,5d,6s,4f,5d,6p,7s and so no.<\/p>\n\n\n\n<p><strong>Aufbau principle<\/strong><\/p>\n\n\n\n<p>The\nelectrons should be filled in energy subshells in order of increasing energy\nvalue. The electrons are first placed in 1s, 2s, 2p and so on.<\/p>\n\n\n\n<p><strong>Pauli\u2019s exclusion\nprinciple<\/strong><\/p>\n\n\n\n<p>Two\nelectrons in the same orbital should have opposite spin.<\/p>\n\n\n\n<p><strong>Hund\u2019s Rule <\/strong><\/p>\n\n\n\n<p>If\ndegenerate orbitals are available and more than one electrons are to be placed\nin them, they should be placed in separate orbitals with the same spin rather\nthan putting them in the same orbital with opposite spins. <\/p>\n\n\n\n<p>For\nexample:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; C = 1s 2s 2p<sub>x<\/sub>\n2p<sub>y<\/sub><\/p>\n\n\n\n<p><strong>References <\/strong><\/p>\n\n\n\n<ol><li><a href=\"https:\/\/courses.lumenlearning.com\/introchem\/chapter\/overview-of-atomic-structure\/\">https:\/\/courses.lumenlearning.com\/introchem\/chapter\/overview-of-atomic-structure\/<\/a><\/li><li><a href=\"https:\/\/en.wikiversity.org\/wiki\/Atomic_structure\">https:\/\/en.wikiversity.org\/wiki\/Atomic_structure<\/a><\/li><li><a href=\"https:\/\/personal.utdallas.edu\/~scortes\/ochem\/OChem1_Lecture\/Class_Materials\/02_atomic_structure.pdf\">https:\/\/personal.utdallas.edu\/~scortes\/ochem\/OChem1_Lecture\/Class_Materials\/02_atomic_structure.pdf<\/a><\/li><li>https:\/\/chem.libretexts.org\/Bookshelves\/Physical_and_Theoretical_Chemistry_Textbook_Maps\/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)\/Atomic_Theory\/The_Atom\/Sub-Atomic_Particles<\/li><\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Definition According to Dalton\u2019s theory atom is smallest particle which could not be divided any further. Atom is the entity that take part in a chemical reaction. For example, He and Ne, etc. have atoms, which exists independently. While atoms of hydrogen, nitrogen and oxygen do not exist independently. An atom is further composed of &#8230; <a title=\"Atomic Structure\" class=\"read-more\" href=\"https:\/\/chemdictionary.org\/atomic-structure\/\" aria-label=\"More on Atomic Structure\">Read more<\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"rating_form_position":"","rating_results_position":"","mr_structured_data_type":""},"categories":[5],"tags":[],"multi-rating":{"mr_rating_results":[{"adjusted_star_result":5,"star_result":5,"total_max_option_value":5,"adjusted_score_result":5,"score_result":5,"percentage_result":100,"adjusted_percentage_result":100,"count":1,"post_id":898}]},"_links":{"self":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts\/898"}],"collection":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/comments?post=898"}],"version-history":[{"count":3,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts\/898\/revisions"}],"predecessor-version":[{"id":938,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/posts\/898\/revisions\/938"}],"wp:attachment":[{"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/media?parent=898"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/categories?post=898"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/chemdictionary.org\/wp-json\/wp\/v2\/tags?post=898"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}