<P> The Russian chemist Dmitri Mendeleev published the first widely recognized periodic table in 1869 . He developed his table to illustrate periodic trends in the properties of the then - known elements . Mendeleev also predicted some properties of then - unknown elements that would be expected to fill gaps in this table . Most of his predictions were proved correct when the elements in question were subsequently discovered . Mendeleev's periodic table has since been expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour . </P> <P> All elements from atomic numbers 1 (hydrogen) to 118 (oganesson) have been discovered or synthesized, with the most recent additions (nihonium, moscovium, tennessine, and oganesson) being confirmed by the International Union of Pure and Applied Chemistry (IUPAC) in 2015 and officially named in 2016: they complete the first seven rows of the periodic table . The first 94 elements exist naturally, although some are found only in trace amounts and were synthesized in laboratories before being found in nature . Elements with atomic numbers from 95 to 118 have only been synthesized in laboratories or nuclear reactors . Synthesis of elements having higher atomic numbers is being pursued . Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories . </P> <Table> <Tr> <Th_colspan="20"> (hide) <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> Periodic table </Th> </Tr> <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 </Td> <Td_colspan="17"> </Td> <Td> Helium 2He </Td> </Tr> <Tr> <Th> </Th> <Td> Lithium 3Li </Td> <Td> Beryllium 4Be </Td> <Td_colspan="11"> </Td> <Td> Boron 5B </Td> <Td> Carbon 6C </Td> <Td> Nitrogen 7N </Td> <Td> Oxygen 8O </Td> <Td> Fluorine 9F </Td> <Td> Neon 10 Ne </Td> </Tr> <Tr> <Th> </Th> <Td> Sodium 11 Na </Td> <Td> Magnesium 12 Mg </Td> <Td_colspan="11"> </Td> <Td> Aluminium 13 Al </Td> <Td> Silicon 14 Si </Td> <Td> Phosphorus 15 P </Td> <Td> Sulfur 16 S </Td> <Td> Chlorine 17 Cl </Td> <Td> Argon 18 Ar </Td> </Tr> <Tr> <Th> </Th> <Td> Potassium 19 K </Td> <Td> Calcium 20 Ca </Td> <Td> Scandium 21 Sc </Td> <Td> </Td> <Td> Titanium 22 Ti </Td> <Td> Vanadium 23 V </Td> <Td> Chromium 24 Cr </Td> <Td> Manganese 25 Mn </Td> <Td> Iron 26 Fe </Td> <Td> Cobalt 27 Co </Td> <Td> Nickel 28 Ni </Td> <Td> Copper 29 Cu </Td> <Td> Zinc 30 Zn </Td> <Td> Gallium 31 Ga </Td> <Td> Germanium 32 Ge </Td> <Td> Arsenic 33 As </Td> <Td> Selenium 34 Se </Td> <Td> Bromine 35 Br </Td> <Td> Krypton 36 Kr </Td> </Tr> <Tr> <Th> 5 </Th> <Td> Rubidium 37 Rb </Td> <Td> Strontium 38 Sr </Td> <Td> Yttrium 39 Y </Td> <Td> </Td> <Td> Zirconium 40 Zr </Td> <Td> Niobium 41 Nb </Td> <Td> Molybdenum 42 Mo </Td> <Td> Technetium 43 Tc </Td> <Td> Ruthenium 44 Ru </Td> <Td> Rhodium 45 Rh </Td> <Td> Palladium 46 Pd </Td> <Td> Silver 47 Ag </Td> <Td> Cadmium 48 Cd </Td> <Td> Indium 49 In </Td> <Td> Tin 50 Sn </Td> <Td> Antimony 51 Sb </Td> <Td> Tellurium 52 Te </Td> <Td> Iodine 53 I </Td> <Td> Xenon 54 Xe </Td> </Tr> <Tr> <Th> 6 </Th> <Td> Caesium 55 Cs </Td> <Td> Barium 56 Ba </Td> <Td> Lanthanum 57 La </Td> <Td> </Td> <Td> Hafnium 72 Hf </Td> <Td> Tantalum 73 Ta </Td> <Td> Tungsten 74 W </Td> <Td> Rhenium 75 Re </Td> <Td> Osmium 76 Os </Td> <Td> Iridium 77 Ir </Td> <Td> Platinum 78 Pt </Td> <Td> Gold 79 Au </Td> <Td> Mercury 80 Hg </Td> <Td> Thallium 81 Tl </Td> <Td> Lead 82 Pb </Td> <Td> Bismuth 83 Bi </Td> <Td> Polonium 84 Po </Td> <Td> Astatine 85 At </Td> <Td> Radon 86 Rn </Td> </Tr> <Tr> <Th> 7 </Th> <Td> Francium 87 Fr </Td> <Td> Radium 88 Ra </Td> <Td> Actinium 89 Ac </Td> <Td> </Td> <Td> Rutherfordium 104 Rf </Td> <Td> Dubnium 105 Db </Td> <Td> Seaborgium 106 Sg </Td> <Td> Bohrium 107 Bh </Td> <Td> Hassium 108 Hs </Td> <Td> Meitnerium 109 Mt </Td> <Td> Darmstadtium 110 Ds </Td> <Td> Roentgenium 111 Rg </Td> <Td> Copernicium 112 Cn </Td> <Td> Nihonium 113 Nh </Td> <Td> Flerovium 114 Fl </Td> <Td> Moscovium 115 Mc </Td> <Td> Livermorium 116 Lv </Td> <Td> Tennessine 117 Ts </Td> <Td> Oganesson 118 Og </Td> </Tr> <Tr> <Td_colspan="20"> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Cerium 58 Ce </Td> <Td> Praseodymium 59 Pr </Td> <Td> Neodymium 60 Nd </Td> <Td> Promethium 61 Pm </Td> <Td> Samarium 62 Sm </Td> <Td> Europium 63 Eu </Td> <Td> Gadolinium 64 Gd </Td> <Td> Terbium 65 Tb </Td> <Td> Dysprosium 66 Dy </Td> <Td> Holmium 67 Ho </Td> <Td> Erbium 68 Er </Td> <Td> Thulium 69 Tm </Td> <Td> Ytterbium 70 Yb </Td> <Td> Lutetium 71 Lu </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Thorium 90 Th </Td> <Td> Protactinium 91 Pa </Td> <Td> Uranium 92 U </Td> <Td> Neptunium 93 Np </Td> <Td> Plutonium 94 Pu </Td> <Td> Americium 95 Am </Td> <Td> Curium 96 Cm </Td> <Td> Berkelium 97 Bk </Td> <Td> Californium 98 Cf </Td> <Td> Einsteinium 99 Es </Td> <Td> Fermium 100 Fm </Td> <Td> Mendelevium 101 Md </Td> <Td> Nobelium 102 No </Td> <Td> Lawrencium 103 Lr </Td> <Td> </Td> </Tr> <Tr> <Td_colspan="20"> </Td> </Tr> <Tr> <Td_colspan="20"> <P> </P> <Table> <Tr> <Td> <Table> <Tr> <Td> black = solid </Td> <Td> green = liquid </Td> <Td> red = gas </Td> <Td> gray = unknown </Td> <Td> Color of the atomic number shows state of matter (at 0 ° C and 1 atm) </Td> </Tr> </Table> </Td> </Tr> <Tr> <Td> <Table> <Tr> <Td> Primordial </Td> <Td> </Td> <Td> From decay </Td> <Td> </Td> <Td> Synthetic </Td> <Td> Border shows natural occurrence of the element </Td> </Tr> </Table> </Td> </Tr> <Tr> <Td> <Table> <Tr> <Td_colspan="11"> Background color shows subcategory in the metal--metalloid--nonmetal trend: </Td> </Tr> <Tr> <Td_colspan="6"> Metal </Td> <Td> Metalloid </Td> <Td_colspan="3"> Nonmetal </Td> <Td> Unknown chemical properties </Td> </Tr> <Tr> <Td> Alkali metal </Td> <Td> Alkaline earth metal </Td> <Td> Lanthanide </Td> <Td> Actinide </Td> <Td> Transition metal </Td> <Td> Post - ​ transition metal </Td> <Td> Polyatomic nonmetal </Td> <Td> Diatomic nonmetal </Td> <Td> Noble gas </Td> </Tr> </Table> </Td> </Tr> </Table> </Td> </Tr> </Table> <Tr> <Th_colspan="20"> (hide) <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> Periodic table </Th> </Tr>

What is the element s on the periodic table