<P> Elements with atomic numbers 1 through 40 are all stable, while those with atomic numbers 41 through 82 (except technetium and promethium) are metastable . The half - lives of these metastable "theoretical radionuclides" are so long (at least 100 million times longer than the estimated age of the universe) that their radioactive decay has yet to be detected by experiment . Elements with atomic numbers 83 through 94 are unstable to the point that their radioactive decay can be detected . Three of these elements, bismuth (element 83), thorium (element 90), and uranium (element 92) have one or more isotopes with half - lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of our solar system . For example, at over 1.9 × 10 years, over a billion times longer than the current estimated age of the universe, bismuth - 209 has the longest known alpha decay half - life of any naturally occurring element . The very heaviest 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half - lives and cannot be produced as daughters of longer - lived elements, and thus they do not occur in nature at all . </P> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <Table> <Tr> <Th> Group </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> 5 </Th> <Th> 6 </Th> <Th> 7 </Th> <Th> 8 </Th> <Th> 9 </Th> <Th> 10 </Th> <Th> 11 </Th> <Th> 12 </Th> <Th> 13 </Th> <Th> 14 </Th> <Th> 15 </Th> <Th> 16 </Th> <Th> 17 </Th> <Th> 18 </Th> </Tr> <Tr> <Td> </Td> <Td> Alkali metals </Td> <Td> Alkaline earth metals </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Pnictogens </Td> <Td> Chalcogens </Td> <Td> Halogens </Td> <Td> Noble gases </Td> </Tr> <Tr> <Th> Period <P> </P> </Th> <Td> Hydrogen 1H ​ 7000100800000000000 ♠ 1.008 </Td> <Td_colspan="17"> </Td> <Td> Helium 2He ​ 7000400260000000000 ♠ 4.0026 </Td> </Tr> <Tr> <Th> </Th> <Td> Lithium 3Li ​ 7000694000000000000 ♠ 6.94 </Td> <Td> Beryllium 4Be ​ 7000901220000000000 ♠ 9.0122 </Td> <Td_colspan="11"> </Td> <Td> Boron 5B ​ 7001108100000000000 ♠ 10.81 </Td> <Td> Carbon 6C ​ 7001120110000000000 ♠ 12.011 </Td> <Td> Nitrogen 7N ​ 7001140070000000000 ♠ 14.007 </Td> <Td> Oxygen 8O ​ 7001159990000000000 ♠ 15.999 </Td> <Td> Fluorine 9F ​ 7001189980000000000 ♠ 18.998 </Td> <Td> Neon 10 Ne ​ 7001201800000000000 ♠ 20.180 </Td> </Tr> <Tr> <Th> </Th> <Td> Sodium 11 Na ​ 7001229899999999999 ♠ 22.990 </Td> <Td> Magnesium 12 Mg ​ 7001243050000000000 ♠ 24.305 </Td> <Td_colspan="11"> </Td> <Td> Aluminium 13 Al ​ 7001269820000000000 ♠ 26.982 </Td> <Td> Silicon 14 Si ​ 7001280850000000000 ♠ 28.085 </Td> <Td> Phosphorus 15 P ​ 7001309740000000000 ♠ 30.974 </Td> <Td> Sulfur 16 S ​ 7001320600000000000 ♠ 32.06 </Td> <Td> Chlorine 17 Cl ​ 7001354500000000000 ♠ 35.45 </Td> <Td> Argon 18 Ar ​ 7001399480000000000 ♠ 39.948 </Td> </Tr> <Tr> <Th> </Th> <Td> Potassium 19 K ​ 7001390980000000000 ♠ 39.098 </Td> <Td> Calcium 20 Ca ​ 7001400780000000000 ♠ 40.078 </Td> <Td> Scandium 21 Sc ​ 7001449560000000000 ♠ 44.956 </Td> <Td> </Td> <Td> Titanium 22 Ti ​ 7001478670000000000 ♠ 47.867 </Td> <Td> Vanadium 23 V ​ 7001509420000000000 ♠ 50.942 </Td> <Td> Chromium 24 Cr ​ 7001519960000000000 ♠ 51.996 </Td> <Td> Manganese 25 Mn ​ 7001549380000000000 ♠ 54.938 </Td> <Td> Iron 26 Fe ​ 7001558450000000000 ♠ 55.845 </Td> <Td> Cobalt 27 Co ​ 7001589330000000000 ♠ 58.933 </Td> <Td> Nickel 28 Ni ​ 7001586930000000000 ♠ 58.693 </Td> <Td> Copper 29 Cu ​ 7001635460000000000 ♠ 63.546 </Td> <Td> Zinc 30 Zn ​ 7001653800000000000 ♠ 65.38 </Td> <Td> Gallium 31 Ga ​ 7001697230000000000 ♠ 69.723 </Td> <Td> Germanium 32 Ge ​ 7001726300000000000 ♠ 72.630 </Td> <Td> Arsenic 33 As ​ 7001749220000000000 ♠ 74.922 </Td> <Td> Selenium 34 Se ​ 7001789710000000000 ♠ 78.971 </Td> <Td> Bromine 35 Br ​ 7001799040000000000 ♠ 79.904 </Td> <Td> Krypton 36 Kr ​ 7001837980000000000 ♠ 83.798 </Td> </Tr> <Tr> <Th> 5 </Th> <Td> Rubidium 37 Rb ​ 7001854680000000000 ♠ 85.468 </Td> <Td> Strontium 38 Sr ​ 7001876200000000000 ♠ 87.62 </Td> <Td> Yttrium 39 Y ​ 7001889060000000000 ♠ 88.906 </Td> <Td> </Td> <Td> Zirconium 40 Zr ​ 7001912240000000000 ♠ 91.224 </Td> <Td> Niobium 41 Nb ​ 7001929060000000000 ♠ 92.906 </Td> <Td> Molybdenum 42 Mo ​ 7001959500000000000 ♠ 95.95 </Td> <Td> Technetium 43 Tc ​ (98) </Td> <Td> Ruthenium 44 Ru ​ 7002101070000000000 ♠ 101.07 </Td> <Td> Rhodium 45 Rh ​ 7002102910000000000 ♠ 102.91 </Td> <Td> Palladium 46 Pd ​ 7002106420000000000 ♠ 106.42 </Td> <Td> Silver 47 Ag ​ 7002107870000000000 ♠ 107.87 </Td> <Td> Cadmium 48 Cd ​ 7002112410000000000 ♠ 112.41 </Td> <Td> Indium 49 In ​ 7002114820000000000 ♠ 114.82 </Td> <Td> Tin 50 Sn ​ 7002118710000000000 ♠ 118.71 </Td> <Td> Antimony 51 Sb ​ 7002121760000000000 ♠ 121.76 </Td> <Td> Tellurium 52 Te ​ 7002127600000000000 ♠ 127.60 </Td> <Td> Iodine 53 I ​ 7002126900000000000 ♠ 126.90 </Td> <Td> Xenon 54 Xe ​ 7002131289999999999 ♠ 131.29 </Td> </Tr> <Tr> <Th> 6 </Th> <Td> Caesium 55 Cs ​ 7002132910000000000 ♠ 132.91 </Td> <Td> Barium 56 Ba ​ 7002137330000000000 ♠ 137.33 </Td> <Td> Lanthanum 57 La ​ 7002138910000000000 ♠ 138.91 </Td> <Td> </Td> <Td> Hafnium 72 Hf ​ 7002178490000000000 ♠ 178.49 </Td> <Td> Tantalum 73 Ta ​ 7002180950000000000 ♠ 180.95 </Td> <Td> Tungsten 74 W ​ 7002183840000000000 ♠ 183.84 </Td> <Td> Rhenium 75 Re ​ 7002186210000000000 ♠ 186.21 </Td> <Td> Osmium 76 Os ​ 7002190230000000000 ♠ 190.23 </Td> <Td> Iridium 77 Ir ​ 7002192220000000000 ♠ 192.22 </Td> <Td> Platinum 78 Pt ​ 7002195080000000000 ♠ 195.08 </Td> <Td> Gold 79 Au ​ 7002196970000000000 ♠ 196.97 </Td> <Td> Mercury 80 Hg ​ 7002200590000000000 ♠ 200.59 </Td> <Td> Thallium 81 Tl ​ 7002204380000000000 ♠ 204.38 </Td> <Td> Lead 82 Pb ​ 7002207200000000000 ♠ 207.2 </Td> <Td> Bismuth 83 Bi ​ 7002208980000000000 ♠ 208.98 </Td> <Td> Polonium 84 Po ​ (209) </Td> <Td> Astatine 85 At ​ (210) </Td> <Td> Radon 86 Rn ​ (222) </Td> </Tr> <Tr> <Th> 7 </Th> <Td> Francium 87 Fr ​ (223) </Td> <Td> Radium 88 Ra ​ (226) </Td> <Td> Actinium 89 Ac ​ (227) </Td> <Td> </Td> <Td> Rutherfordium 104 Rf ​ (267) </Td> <Td> Dubnium 105 Db ​ (268) </Td> <Td> Seaborgium 106 Sg ​ (269) </Td> <Td> Bohrium 107 Bh ​ (270) </Td> <Td> Hassium 108 Hs ​ (270) </Td> <Td> Meitnerium 109 Mt ​ (278) </Td> <Td> Darmstadtium 110 Ds ​ (281) </Td> <Td> Roentgenium 111 Rg ​ (282) </Td> <Td> Copernicium 112 Cn ​ (285) </Td> <Td> Nihonium 113 Nh ​ (286) </Td> <Td> Flerovium 114 Fl ​ (289) </Td> <Td> Moscovium 115 Mc ​ (290) </Td> <Td> Livermorium 116 Lv ​ (293) </Td> <Td> Tennessine 117 Ts ​ (294) </Td> <Td> Oganesson 118 Og ​ (294) </Td> </Tr> <Tr> <Td_colspan="20"> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Cerium 58 Ce ​ 7002140120000000000 ♠ 140.12 </Td> <Td> Praseodymium 59 Pr ​ 7002140910000000000 ♠ 140.91 </Td> <Td> Neodymium 60 Nd ​ 7002144240000000000 ♠ 144.24 </Td> <Td> Promethium 61 Pm ​ (145) </Td> <Td> Samarium 62 Sm ​ 7002150360000000000 ♠ 150.36 </Td> <Td> Europium 63 Eu ​ 7002151960000000000 ♠ 151.96 </Td> <Td> Gadolinium 64 Gd ​ 7002157250000000000 ♠ 157.25 </Td> <Td> Terbium 65 Tb ​ 7002158930000000000 ♠ 158.93 </Td> <Td> Dysprosium 66 Dy ​ 7002162500000000000 ♠ 162.50 </Td> <Td> Holmium 67 Ho ​ 7002164930000000000 ♠ 164.93 </Td> <Td> Erbium 68 Er ​ 7002167260000000000 ♠ 167.26 </Td> <Td> Thulium 69 Tm ​ 7002168930000000000 ♠ 168.93 </Td> <Td> Ytterbium 70 Yb ​ 7002173050000000000 ♠ 173.05 </Td> <Td> Lutetium 71 Lu ​ 7002174970000000000 ♠ 174.97 </Td> <Td> </Td> </Tr> <Tr> <Td_colspan="4"> </Td> <Td> </Td> <Td> Thorium 90 Th ​ 7002232040000000000 ♠ 232.04 </Td> <Td> Protactinium 91 Pa ​ 7002231040000000000 ♠ 231.04 </Td> <Td> Uranium 92 U ​ 7002238030000000000 ♠ 238.03 </Td> <Td> Neptunium 93 Np ​ (237) </Td> <Td> Plutonium 94 Pu ​ (244) </Td> <Td> Americium 95 Am ​ (243) </Td> <Td> Curium 96 Cm ​ (247) </Td> <Td> Berkelium 97 Bk ​ (247) </Td> <Td> Californium 98 Cf ​ (251) </Td> <Td> Einsteinium 99 Es ​ (252) </Td> <Td> Fermium 100 Fm ​ (257) </Td> <Td> Mendelevium 101 Md ​ (258) </Td> <Td> Nobelium 102 No ​ (259) </Td> <Td> Lawrencium 103 Lr ​ (266) </Td> </Tr> </Table> <Tr> <Th> Group </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> 5 </Th> <Th> 6 </Th> <Th> 7 </Th> <Th> 8 </Th> <Th> 9 </Th> <Th> 10 </Th> <Th> 11 </Th> <Th> 12 </Th> <Th> 13 </Th> <Th> 14 </Th> <Th> 15 </Th> <Th> 16 </Th> <Th> 17 </Th> <Th> 18 </Th> </Tr>

1 to 40 elements with symbols and atomic number
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