Periodic Table of Elements
| Z | Symbol | Element | Standard atomic weight | Category |
|---|---|---|---|---|
| 1 | H | hydrogen | [1.00784,1.00811] | reactive nonmetal |
| 2 | He | helium | 4.002602(2) | noble gas |
| 3 | Li | lithium | [6.938,6.997] | alkali metal |
| 4 | Be | beryllium | 9.0121831(5) | alkaline earth metal |
| 5 | B | boron | [10.806,10.821] | metalloid |
| 6 | C | carbon | [12.0096,12.0116] | reactive nonmetal |
| 7 | N | nitrogen | [14.00643,14.00728] | reactive nonmetal |
| 8 | O | oxygen | [15.99903,15.99977] | reactive nonmetal |
| 9 | F | fluorine | 18.998403162(5) | halogen |
| 10 | Ne | neon | 20.1797(6) | noble gas |
| 11 | Na | sodium | 22.98976928(2) | alkali metal |
| 12 | Mg | magnesium | [24.304,24.307] | alkaline earth metal |
| 13 | Al | aluminium | 26.9815384(3) | post-transition metal |
| 14 | Si | silicon | [28.084,28.086] | metalloid |
| 15 | P | phosphorus | 30.973761998(5) | reactive nonmetal |
| 16 | S | sulfur | [32.059,32.076] | reactive nonmetal |
| 17 | Cl | chlorine | [35.446,35.457] | halogen |
| 18 | Ar | argon | [39.792,39.963] | noble gas |
| 19 | K | potassium | 39.0983(1) | alkali metal |
| 20 | Ca | calcium | 40.078(4) | alkaline earth metal |
| 21 | Sc | scandium | 44.955907(4) | transition metal |
| 22 | Ti | titanium | 47.867(1) | transition metal |
| 23 | V | vanadium | 50.9415(1) | transition metal |
| 24 | Cr | chromium | 51.9961(6) | transition metal |
| 25 | Mn | manganese | 54.938043(2) | transition metal |
| 26 | Fe | iron | 55.845(2) | transition metal |
| 27 | Co | cobalt | 58.933194(3) | transition metal |
| 28 | Ni | nickel | 58.6934(4) | transition metal |
| 29 | Cu | copper | 63.546(3) | transition metal |
| 30 | Zn | zinc | 65.38(2) | transition metal |
| 31 | Ga | gallium | 69.723(1) | post-transition metal |
| 32 | Ge | germanium | 72.630(8) | metalloid |
| 33 | As | arsenic | 74.921595(6) | metalloid |
| 34 | Se | selenium | 78.971(8) | reactive nonmetal |
| 35 | Br | bromine | [79.901,79.907] | halogen |
| 36 | Kr | krypton | 83.798(2) | noble gas |
| 37 | Rb | rubidium | 85.4678(3) | alkali metal |
| 38 | Sr | strontium | 87.62(1) | alkaline earth metal |
| 39 | Y | yttrium | 88.905838(2) | transition metal |
| 40 | Zr | zirconium | 91.222(3) | transition metal |
| 41 | Nb | niobium | 92.90637(1) | transition metal |
| 42 | Mo | molybdenum | 95.95(1) | transition metal |
| 43 | Tc | technetium | — | transition metal |
| 44 | Ru | ruthenium | 101.07(2) | transition metal |
| 45 | Rh | rhodium | 102.90549(2) | transition metal |
| 46 | Pd | palladium | 106.42(1) | transition metal |
| 47 | Ag | silver | 107.8682(2) | transition metal |
| 48 | Cd | cadmium | 112.414(4) | transition metal |
| 49 | In | indium | 114.818(1) | post-transition metal |
| 50 | Sn | tin | 118.710(7) | post-transition metal |
| 51 | Sb | antimony | 121.760(1) | metalloid |
| 52 | Te | tellurium | 127.60(3) | metalloid |
| 53 | I | iodine | 126.90447(3) | halogen |
| 54 | Xe | xenon | 131.293(6) | noble gas |
| 55 | Cs | caesium | 132.90545196(6) | alkali metal |
| 56 | Ba | barium | 137.327(7) | alkaline earth metal |
| 57 | La | lanthanum | 138.90547(7) | lanthanide |
| 58 | Ce | cerium | 140.116(1) | lanthanide |
| 59 | Pr | praseodymium | 140.90766(1) | lanthanide |
| 60 | Nd | neodymium | 144.242(3) | lanthanide |
| 61 | Pm | promethium | — | lanthanide |
| 62 | Sm | samarium | 150.36(2) | lanthanide |
| 63 | Eu | europium | 151.964(1) | lanthanide |
| 64 | Gd | gadolinium | 157.249(2) | lanthanide |
| 65 | Tb | terbium | 158.925354(7) | lanthanide |
| 66 | Dy | dysprosium | 162.500(1) | lanthanide |
| 67 | Ho | holmium | 164.930329(5) | lanthanide |
| 68 | Er | erbium | 167.259(3) | lanthanide |
| 69 | Tm | thulium | 168.934219(5) | lanthanide |
| 70 | Yb | ytterbium | 173.045(10) | lanthanide |
| 71 | Lu | lutetium | 174.96669(5) | lanthanide |
| 72 | Hf | hafnium | 178.486(6) | transition metal |
| 73 | Ta | tantalum | 180.94788(2) | transition metal |
| 74 | W | tungsten | 183.84(1) | transition metal |
| 75 | Re | rhenium | 186.207(1) | transition metal |
| 76 | Os | osmium | 190.23(3) | transition metal |
| 77 | Ir | iridium | 192.217(2) | transition metal |
| 78 | Pt | platinum | 195.084(9) | transition metal |
| 79 | Au | gold | 196.966570(4) | transition metal |
| 80 | Hg | mercury | 200.592(3) | transition metal |
| 81 | Tl | thallium | [204.382,204.385] | post-transition metal |
| 82 | Pb | lead | [206.14,207.94] | post-transition metal |
| 83 | Bi | bismuth | 208.98040(1) | post-transition metal |
| 84 | Po | polonium | — | post-transition metal |
| 85 | At | astatine | — | halogen |
| 86 | Rn | radon | — | noble gas |
| 87 | Fr | francium | — | alkali metal |
| 88 | Ra | radium | — | alkaline earth metal |
| 89 | Ac | actinium | — | actinide |
| 90 | Th | thorium | 232.0377(4) | actinide |
| 91 | Pa | protactinium | 231.03588(1) | actinide |
| 92 | U | uranium | 238.02891(3) | actinide |
| 93 | Np | neptunium | — | actinide |
| 94 | Pu | plutonium | — | actinide |
| 95 | Am | americium | — | actinide |
| 96 | Cm | curium | — | actinide |
| 97 | Bk | berkelium | — | actinide |
| 98 | Cf | californium | — | actinide |
| 99 | Es | einsteinium | — | actinide |
| 100 | Fm | fermium | — | actinide |
| 101 | Md | mendelevium | — | actinide |
| 102 | No | nobelium | — | actinide |
| 103 | Lr | lawrencium | — | actinide |
| 104 | Rf | rutherfordium | — | transition metal |
| 105 | Db | dubnium | — | transition metal |
| 106 | Sg | seaborgium | — | transition metal |
| 107 | Bh | bohrium | — | transition metal |
| 108 | Hs | hassium | — | transition metal |
| 109 | Mt | meitnerium | — | transition metal |
| 110 | Ds | darmstadtium | — | transition metal |
| 111 | Rg | roentgenium | — | transition metal |
| 112 | Cn | copernicium | — | transition metal |
| 113 | Nh | nihonium | — | transition metal |
| 114 | Fl | flerovium | — | transition metal |
| 115 | Mc | moscovium | — | transition metal |
| 116 | Lv | livermorium | — | transition metal |
| 117 | Ts | tennessine | — | halogen |
| 118 | Og | oganesson | — | noble gas |
The periodic table holds 118 confirmed elements, and the table runs the full ladder from hydrogen (Z=1) to oganesson (Z=118). The numbering is the proton count - change Z and you change the element - while the atomic-weight column carries the honest complication: most elements get a single standard weight, but twelve (hydrogen, carbon, nitrogen, oxygen and their isotope-variable siblings) carry bracketed ranges because nature itself varies their isotope mix by source.
The category column is the periodic law made visible: the alkali metals in column one (lithium to francium) all trade one electron violently; the noble gases at the far right (helium to radon, with oganesson predicted to break the pattern) refuse to react; the halogens beside them are the aggressive electron-thieves that pair with the alkalis. The lanthanides and actinides sit in detached rows because their f-electrons run the same outer-shell story twice - the rare earths and the radioactive heavyweights.
The last nine elements (104-118, rutherfordium through oganesson) are the synthetic frontier: made atom-by-atom in particle accelerators, named for the people and places of their discovery, and gone in seconds or milliseconds. Oganesson (2016, named for Yuri Oganessian) closed period seven and remains the heaviest element ever confirmed - chemically predicted to be a noble gas that ignores its family's rules.
How to use
- Find any element by Z, symbol or name: the weight column gives the IUPAC standard atomic weight - read values like 35.45 (chlorine) as the laboratory-average mass, and bracketed ranges like hydrogen's [1.008] as 'depends on the sample.'
- Use the category column for reactivity predictions: alkali + halogen = salt (table salt is Na-Cl); two noble gases = nothing, ever; transition metals in the middle = the conductors, catalysts and structural metals of industry.
- Answer the classic questions: the heaviest natural element is uranium (92); plutonium (94) occurs naturally only in traces; the heaviest confirmed element is oganesson (118); the rarest stable-adjacent natural element is astatine (85) - the Earth's inventory at any moment is under a gram.
- Read the weight column's footnote as a chemistry lesson: bracketed ranges exist because isotopic ratios differ between, say, deep-ocean and volcanic hydrogen - the twelve range elements are the ones the IUPAC refuses to pin to a single number.
Frequently asked questions
How many elements are in the periodic table?
118 confirmed, from hydrogen (Z=1) to oganesson (Z=118). The first 94 occur naturally (in traces for the heaviest); elements 95-118 are synthetic, produced in accelerators and reactors. The seven-period table completed in 2016 when the names nihonium, moscovium, tennessine and oganesson were ratified.
What is the heaviest element?
Oganesson (Z=118), synthesized at Dubna in 2002 and named in 2016 - a few atoms at a time, with a half-life under a millisecond. The heaviest element with meaningful quantities is uranium (Z=92); plutonium (Z=94) sits between, occurring naturally only as trace signatures in ores.
Why do some atomic weights have ranges instead of single values?
Isotope variation: twelve elements (hydrogen, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, argon, potassium, bromine, thallium... per IUPAC) show different isotope ratios in different natural sources, so their weight genuinely depends on the sample - the bracketed range is the span of real-world values. This is why chlorine is variously quoted at 35.45.
What are the element categories in the table?
Alkali metals and alkaline earths (columns 1-2, reactive metals), transition metals (the industrial middle block), post-transition metals, metalloids (the semiconductor frontier: boron, silicon, germanium...), reactive nonmetals, halogens (the salt-formers), noble gases (the inert column), plus the two detached blocks: lanthanides (the rare earths) and actinides (uranium's radioactive family).