In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present). The number of protons determines how many electrons surround the nucleus, and it is the arrangement of these electrons that determines most of the chemical behavior of an element.
In a periodic table arranged in order of increasing atomic number, elements having similar chemical properties naturally line up in the same column (group). For instance, all of the elements in Group 1A are relatively soft metals, react violently with water, and form 1+ charges; all of the elements in Group 8A are unreactive, monatomic gases at room temperature, etc. In other words, there is a periodic repetition of the properties of the chemical elements with increasing mass.
In the original periodic table published by Dimitri Mendeleev in 1869, the elements were arranged according to increasing atomic mass—at that time, the nucleus had not yet been discovered, and there was no understanding at all of the interior structure of the atom, so atomic mass was the only guide to use. Once the structure of the nucleus was understood, it became clear that it was the atomic number that governed the properties of the elements.
The Elements, sorted by Atomic NumberAtomic
NumberSymbolNameAtomic Mass
(amu, g/mol)H Hydrogen 1.007972 He Helium 4.002603 Li Lithium6.9414 Be Beryllium 9.012185B Boron 10.816C Carbon 12.0117N Nitrogen 14.00678O Oxygen 15.99949 F Fluorine 18.99840310 Ne Neon 20.17911Na Sodium 22.9897712Mg Magnesium 24.30513 Al Aluminum26.9815414 Si Silicon28.085515 P Phosphorus30.9737616S Sulfur32.0617 Cl Chlorine35.45318 Ar Argon39.94819 K Potassium39.098320 Ca Calcium40.0821 Sc Scandium44.955922 Ti Titanium47.9023 V Vanadium50.941524 Cr Chromium51.99625 Mn Manganese54.938026 FeIron55.84727 Co Cobalt58.933228 Ni Nickel58.7029 Cu Copper63.54630Zn Zinc65.3831 Ga Gallium69.7232 Ge Germanium72.5933 As Arsenic74.921634 Se Selenium78.9635Br Bromine79.90436 Kr Krypton83.8037 Rb Rubidium85.467838 Sr Strontium87.6239 Y Yttrium88.905940 Zr Zirconium91.2241 Nb Niobium92.906442 Mo Molybdenum95.9443 Tc Technetium(98)44 Ru Ruthenium101.0745 Rh Rhodium102.905546 Pd Palladium106.447 Ag Silver107.86848 Cd Cadmium112.4149 In Indium114.8250 Sn Tin118.6951 Sb Antimony121.7552Te Tellurium 127.6053 I Iodine126.904554 Xe Xenon131.3055 Cs Cesium132.905456 Ba Barium137.3357 La Lanthanum138.905558 Ce Cerium140.1259 Pr Praseodymium140.907760 Nd Neodymium144.2461 Pm Promethium(145)62 Sm Samarium150.463 Eu Europium 151.9664 Gd Gadolinium157.2565 Tb Terbium 158.925466 Dy Dysprosium162.5067Ho Holmium164.930468Er Erbium167.2669 Tm Thulium168.934270 Yb Ytterbium 173.0471Lu Lutetium 174.96772 Hf Hafnium 178.4973 Ta Tantalum 180.947974 W Tungsten183.8575 Re Rhenium186.20776 Os Osmium190.277Ir Iridium 192.2278 Pt Platinum195.0979 Au Gold196.966580 Hg Mercury200.5981 Tl Thallium 204.3782 Pb Lead207.283 Bi Bismuth208.980484 Po Polonium(209)85 At Astatine(210)86 Rn Radon(222)87 Fr Francium(223)88 Ra Radium226.025489Ac Actinium 227.027890 Th Thorium232.038191 Pa Protactinium 231.035992 U Uranium 238.02993 Np Neptunium 237.048294 Pu Plutonium(242) 95 Am Americium(243) 96 Cm Curium(247) 97 Bk Berkelium(247) 98 Cf Californium (251)99 Es Einsteinium (252)100Fm Fermium (257)101Md Mendelevium( 258)102No Nobelium (250)103Lr Lawrencium (260)104Rf Rutherfordium (261)105 Db Dubnium (262)106 Sg Seaborgium (263) 107 Bh Bohrium(262)108 Hs Hassium (255)109 Mt Meitnerium (256) 110 Ds Darmstadtium (269) 111 Rg Roentgenium(272 )112 Uub Ununbiium (277) 113————114 Uuq Ununquadium------
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The Great World Of Chemistry
No FicciónThe World Of Microbes Is An Important Part Of Chemistry. It Is The Thing From Which We Evolve. We Do Not Know Much About These Things So Let Us Explore Into The World Of Chemistry.
