<P> The adult human body averages ~ 53% water . This varies substantially by age, sex, and adiposity . In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ± 6% for females and 58 ± 8% water for males . Water is ~ 11% hydrogen by mass but ~ 67% hydrogen by atomic percent, and these numbers along with the complementary% numbers for oxygen in water, are the largest contributors to overall mass and atomic composition figures . Because of water content, the human body contains more oxygen by mass than any other element, but more hydrogen by atom - fraction than any element . </P> <P> The elements listed below as "Essential in humans" are those listed by the (US) Food and Drug Administration as essential nutrients, as well as six additional elements: oxygen, carbon, hydrogen, and nitrogen (the fundamental building blocks of life on Earth), sulfur (essential to all cells) and cobalt (a necessary component of vitamin B). Elements listed as "Possibly" or "Probably" essential are those cited by the National Research Council (United States) as beneficial to human health and possibly or probably essential . </P> <Table> <Tr> <Th> Atomic number </Th> <Th> Element </Th> <Th> Fraction of mass </Th> <Th> Mass (kg) </Th> <Th> Atomic percent </Th> <Th> Essential in humans </Th> <Th> Negative effects of excess </Th> <Th> Group </Th> </Tr> <Tr> <Td> 8 </Td> <Td> Oxygen </Td> <Td> 0.65 </Td> <Td> 43 </Td> <Td> 24 </Td> <Td> Yes (e.g. water, electron acceptor) </Td> <Td> Reactive oxygen species </Td> <Td> 16 </Td> </Tr> <Tr> <Td> 6 </Td> <Td> Carbon </Td> <Td> 0.18 </Td> <Td> 16 </Td> <Td> 12 </Td> <Td> Yes (organic compounds) </Td> <Td> </Td> <Td> 14 </Td> </Tr> <Tr> <Td> </Td> <Td> Hydrogen </Td> <Td> 0.10 </Td> <Td> 7 </Td> <Td> 62 </Td> <Td> Yes (e.g. water) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 7 </Td> <Td> Nitrogen </Td> <Td> 0.03 </Td> <Td> 1.8 </Td> <Td> 1.1 </Td> <Td> Yes (e.g. DNA and amino acids) </Td> <Td> </Td> <Td> 15 </Td> </Tr> <Tr> <Td> 20 </Td> <Td> Calcium </Td> <Td> 0.014 </Td> <Td> 1.0 </Td> <Td> 0.22 </Td> <Td> Yes (e.g. Calmodulin and Hydroxylapatite in bones) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 15 </Td> <Td> Phosphorus </Td> <Td> 0.011 </Td> <Td> 0.78 </Td> <Td> 0.22 </Td> <Td> Yes (e.g. DNA and phosphorylation) </Td> <Td> white allotrope highly toxic </Td> <Td> 15 </Td> </Tr> <Tr> <Td> 19 </Td> <Td> Potassium </Td> <Td> 6997200000000000000 ♠ 2.0 × 10 </Td> <Td> 0.14 </Td> <Td> 0.033 </Td> <Td> Yes (e.g. Na / K - ATPase) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 16 </Td> <Td> Sulfur </Td> <Td> 6997250000000000000 ♠ 2.5 × 10 </Td> <Td> 0.14 </Td> <Td> 0.038 </Td> <Td> Yes (e.g. Cysteine, Methionine, Biotin, Thiamine) </Td> <Td> </Td> <Td> 16 </Td> </Tr> <Tr> <Td> 11 </Td> <Td> Sodium </Td> <Td> 6997150000000000000 ♠ 1.5 × 10 </Td> <Td> 0.10 </Td> <Td> 0.037 </Td> <Td> Yes (e.g. Na / K - ATPase) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 17 </Td> <Td> Chlorine </Td> <Td> 6997150000000000000 ♠ 1.5 × 10 </Td> <Td> 0.095 </Td> <Td> 0.024 </Td> <Td> Yes (e.g. Cl - transporting ATPase) </Td> <Td> </Td> <Td> 17 </Td> </Tr> <Tr> <Td> 12 </Td> <Td> Magnesium </Td> <Td> 6996500000000000000 ♠ 500 × 10 </Td> <Td> 0.019 </Td> <Td> 0.0070 </Td> <Td> Yes (e.g. binding to ATP and other nucleotides) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 26 </Td> <Td> Iron * </Td> <Td> 6995600000000000000 ♠ 60 × 10 </Td> <Td> 0.0042 </Td> <Td> 0.00067 </Td> <Td> Yes (e.g. Hemoglobin, Cytochromes) </Td> <Td> </Td> <Td> 8 </Td> </Tr> <Tr> <Td> 9 </Td> <Td> Fluorine </Td> <Td> 6995370000000000000 ♠ 37 × 10 </Td> <Td> 0.0026 </Td> <Td> 0.0012 </Td> <Td> Yes (AUS, NZ), No (US, EU), Maybe (WHO) </Td> <Td> toxic in high amounts </Td> <Td> 17 </Td> </Tr> <Tr> <Td> 30 </Td> <Td> Zinc </Td> <Td> 6995320000000000000 ♠ 32 × 10 </Td> <Td> 0.0023 </Td> <Td> 0.00031 </Td> <Td> Yes (e.g. Zinc finger proteins) </Td> <Td> </Td> <Td> 12 </Td> </Tr> <Tr> <Td> 14 </Td> <Td> Silicon </Td> <Td> 6995199999999999999 ♠ 20 × 10 </Td> <Td> 0.0010 </Td> <Td> 0.0058 </Td> <Td> Possibly </Td> <Td> </Td> <Td> 14 </Td> </Tr> <Tr> <Td> 37 </Td> <Td> Rubidium </Td> <Td> 6994459999999999999 ♠ 4.6 × 10 </Td> <Td> 0.00068 </Td> <Td> 0.000033 </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 38 </Td> <Td> Strontium </Td> <Td> 6994459999999999999 ♠ 4.6 × 10 </Td> <Td> 0.00032 </Td> <Td> 0.000033 </Td> <Td>---- </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 35 </Td> <Td> Bromine </Td> <Td> 6994290000000000000 ♠ 2.9 × 10 </Td> <Td> 0.00026 </Td> <Td> 0.000030 </Td> <Td>---- </Td> <Td> </Td> <Td> 17 </Td> </Tr> <Tr> <Td> 82 </Td> <Td> Lead </Td> <Td> 6994169999999999999 ♠ 1.7 × 10 </Td> <Td> 0.00012 </Td> <Td> 0.0000045 </Td> <Td> No </Td> <Td> toxic </Td> <Td> 14 </Td> </Tr> <Tr> <Td> 29 </Td> <Td> Copper </Td> <Td> 6994100000000000000 ♠ 1 × 10 </Td> <Td> 0.000072 </Td> <Td> 0.0000104 </Td> <Td> Yes (e.g. copper proteins) </Td> <Td> </Td> <Td> 11 </Td> </Tr> <Tr> <Td> 13 </Td> <Td> Aluminium </Td> <Td> 6993870000000000000 ♠ 870 × 10 </Td> <Td> 0.000060 </Td> <Td> 0.000015 </Td> <Td> No </Td> <Td> </Td> <Td> 13 </Td> </Tr> <Tr> <Td> 48 </Td> <Td> Cadmium </Td> <Td> 6993720000000000000 ♠ 720 × 10 </Td> <Td> 0.000050 </Td> <Td> 0.0000045 </Td> <Td> No </Td> <Td> toxic </Td> <Td> 12 </Td> </Tr> <Tr> <Td> 58 </Td> <Td> Cerium </Td> <Td> 6993570000000000000 ♠ 570 × 10 </Td> <Td> 0.000040 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 56 </Td> <Td> Barium </Td> <Td> 6993310000000000000 ♠ 310 × 10 </Td> <Td> 0.000022 </Td> <Td> 0.0000012 </Td> <Td> No </Td> <Td> toxic in higher amounts </Td> <Td> </Td> </Tr> <Tr> <Td> 50 </Td> <Td> Tin </Td> <Td> 6993240000000000000 ♠ 240 × 10 </Td> <Td> 0.000020 </Td> <Td> 6993600000000000000 ♠ 6.0 × 10 </Td> <Td> No </Td> <Td> </Td> <Td> 14 </Td> </Tr> <Tr> <Td> 53 </Td> <Td> Iodine </Td> <Td> 6993160000000000000 ♠ 160 × 10 </Td> <Td> 0.000020 </Td> <Td> 6993750000000000000 ♠ 7.5 × 10 </Td> <Td> Yes (e.g. thyroxine, triiodothyronine) </Td> <Td> </Td> <Td> 17 </Td> </Tr> <Tr> <Td> 22 </Td> <Td> Titanium </Td> <Td> 6993130000000000000 ♠ 130 × 10 </Td> <Td> 0.000020 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 5 </Td> <Td> Boron </Td> <Td> 6993690000000000000 ♠ 690 × 10 </Td> <Td> 0.000018 </Td> <Td> 0.0000030 </Td> <Td> Probably </Td> <Td> </Td> <Td> 13 </Td> </Tr> <Tr> <Td> 34 </Td> <Td> Selenium </Td> <Td> 6993190000000000000 ♠ 190 × 10 </Td> <Td> 0.000015 </Td> <Td> 6992450000000000000 ♠ 4.5 × 10 </Td> <Td> Yes </Td> <Td> toxic in higher amounts </Td> <Td> 16 </Td> </Tr> <Tr> <Td> 28 </Td> <Td> Nickel </Td> <Td> 6993140000000000000 ♠ 140 × 10 </Td> <Td> 0.000015 </Td> <Td> 0.0000015 </Td> <Td> Probably </Td> <Td> toxic in higher amounts </Td> <Td> 10 </Td> </Tr> <Tr> <Td> 24 </Td> <Td> Chromium </Td> <Td> 6992240000000000000 ♠ 24 × 10 </Td> <Td> 0.000014 </Td> <Td> 6992890000000000000 ♠ 8.9 × 10 </Td> <Td> Yes </Td> <Td> </Td> <Td> 6 </Td> </Tr> <Tr> <Td> 25 </Td> <Td> Manganese </Td> <Td> 6993170000000000000 ♠ 170 × 10 </Td> <Td> 0.000012 </Td> <Td> 0.0000015 </Td> <Td> Yes (e.g. Mn - SOD) </Td> <Td> </Td> <Td> 7 </Td> </Tr> <Tr> <Td> 33 </Td> <Td> Arsenic </Td> <Td> 6993260000000000000 ♠ 260 × 10 </Td> <Td> 0.000007 </Td> <Td> 6992890000000000000 ♠ 8.9 × 10 </Td> <Td> Possibly </Td> <Td> toxic in higher amounts </Td> <Td> 15 </Td> </Tr> <Tr> <Td> </Td> <Td> Lithium </Td> <Td> 6992310000000000000 ♠ 31 × 10 </Td> <Td> 0.000007 </Td> <Td> 0.0000015 </Td> <Td> Yes (intercorrelated with the functions of several enzymes, hormones and vitamins) </Td> <Td> toxic in higher amounts </Td> <Td> </Td> </Tr> <Tr> <Td> 80 </Td> <Td> Mercury </Td> <Td> 6993190000000000000 ♠ 190 × 10 </Td> <Td> 0.000006 </Td> <Td> 6992890000000000000 ♠ 8.9 × 10 </Td> <Td> No </Td> <Td> toxic </Td> <Td> 12 </Td> </Tr> <Tr> <Td> 55 </Td> <Td> Caesium </Td> <Td> 6992210000000000000 ♠ 21 × 10 </Td> <Td> 0.000006 </Td> <Td> 6993100000000000000 ♠ 1.0 × 10 </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 42 </Td> <Td> Molybdenum </Td> <Td> 6993130000000000000 ♠ 130 × 10 </Td> <Td> 0.000005 </Td> <Td> 6992450000000000000 ♠ 4.5 × 10 </Td> <Td> Yes (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase) </Td> <Td> </Td> <Td> 6 </Td> </Tr> <Tr> <Td> 32 </Td> <Td> Germanium </Td> <Td> </Td> <Td> 6994499999999999999 ♠ 5 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 14 </Td> </Tr> <Tr> <Td> 27 </Td> <Td> Cobalt </Td> <Td> 6992210000000000000 ♠ 21 × 10 </Td> <Td> 0.000003 </Td> <Td> 6993300000000000000 ♠ 3.0 × 10 </Td> <Td> Yes (cobalamin, B) </Td> <Td> </Td> <Td> 9 </Td> </Tr> <Tr> <Td> 51 </Td> <Td> Antimony </Td> <Td> 6993110000000000000 ♠ 110 × 10 </Td> <Td> 0.000002 </Td> <Td> </Td> <Td> No </Td> <Td> toxic </Td> <Td> 15 </Td> </Tr> <Tr> <Td> 47 </Td> <Td> Silver </Td> <Td> 6992100000000000000 ♠ 10 × 10 </Td> <Td> 0.000002 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 11 </Td> </Tr> <Tr> <Td> 41 </Td> <Td> Niobium </Td> <Td> 6994160000000000000 ♠ 1600 × 10 </Td> <Td> 0.0000015 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 5 </Td> </Tr> <Tr> <Td> 40 </Td> <Td> Zirconium </Td> <Td> 6994600000000000000 ♠ 6 × 10 </Td> <Td> 0.000001 </Td> <Td> 6993300000000000000 ♠ 3.0 × 10 </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 57 </Td> <Td> Lanthanum </Td> <Td> 6994137000000000000 ♠ 1370 × 10 </Td> <Td> 6993800000000000000 ♠ 8 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 52 </Td> <Td> Tellurium </Td> <Td> 6993120000000000000 ♠ 120 × 10 </Td> <Td> 6993700000000000000 ♠ 7 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 16 </Td> </Tr> <Tr> <Td> 31 </Td> <Td> Gallium </Td> <Td> </Td> <Td> 6993700000000000000 ♠ 7 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 13 </Td> </Tr> <Tr> <Td> 39 </Td> <Td> Yttrium </Td> <Td> </Td> <Td> 6993600000000000000 ♠ 6 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 83 </Td> <Td> Bismuth </Td> <Td> </Td> <Td> 6993500000000000000 ♠ 5 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 15 </Td> </Tr> <Tr> <Td> 81 </Td> <Td> Thallium </Td> <Td> </Td> <Td> 6993500000000000000 ♠ 5 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> highly toxic </Td> <Td> 13 </Td> </Tr> <Tr> <Td> 49 </Td> <Td> Indium </Td> <Td> </Td> <Td> 6993400000000000000 ♠ 4 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 13 </Td> </Tr> <Tr> <Td> 79 </Td> <Td> Gold </Td> <Td> 6991300000000000000 ♠ 3 × 10 </Td> <Td> 6993200000000000000 ♠ 2 × 10 </Td> <Td> 6993300000000000000 ♠ 3.0 × 10 </Td> <Td> No </Td> <Td> uncoated nanoparticles possibly genotoxic </Td> <Td> 11 </Td> </Tr> <Tr> <Td> 21 </Td> <Td> Scandium </Td> <Td> </Td> <Td> 6993200000000000000 ♠ 2 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 73 </Td> <Td> Tantalum </Td> <Td> </Td> <Td> 6993200000000000000 ♠ 2 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 5 </Td> </Tr> <Tr> <Td> 23 </Td> <Td> Vanadium </Td> <Td> 6993260000000000000 ♠ 260 × 10 </Td> <Td> 6993110000000000000 ♠ 1.1 × 10 </Td> <Td> 6992120000000000000 ♠ 1.2 × 10 </Td> <Td> Possibly (suggested osteo - metabolism (bone) growth factor) </Td> <Td> </Td> <Td> 5 </Td> </Tr> <Tr> <Td> 90 </Td> <Td> Thorium </Td> <Td> </Td> <Td> 6993100000000000000 ♠ 1 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> toxic, radioactive </Td> <Td> </Td> </Tr> <Tr> <Td> 92 </Td> <Td> Uranium </Td> <Td> </Td> <Td> 6993100000000000000 ♠ 1 × 10 </Td> <Td> 6991300000000000000 ♠ 3.0 × 10 </Td> <Td> No </Td> <Td> toxic, radioactive </Td> <Td> </Td> </Tr> <Tr> <Td> 62 </Td> <Td> Samarium </Td> <Td> </Td> <Td> 6992500000000000000 ♠ 5.0 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 74 </Td> <Td> Tungsten </Td> <Td> </Td> <Td> 6992200000000000000 ♠ 2.0 × 10 </Td> <Td> </Td> <Td> No </Td> <Td> </Td> <Td> 6 </Td> </Tr> <Tr> <Td> </Td> <Td> Beryllium </Td> <Td> </Td> <Td> 6992360000000000000 ♠ 3.6 × 10 </Td> <Td> 6992450000000000000 ♠ 4.5 × 10 </Td> <Td> No </Td> <Td> toxic in higher amounts </Td> <Td> </Td> </Tr> <Tr> <Td> 88 </Td> <Td> Radium </Td> <Td> </Td> <Td> 6986300000000000000 ♠ 3 × 10 </Td> <Td> 6983100000000000000 ♠ 1 × 10 </Td> <Td> No </Td> <Td> toxic, radioactive </Td> <Td> </Td> </Tr> </Table> <Tr> <Th> Atomic number </Th> <Th> Element </Th> <Th> Fraction of mass </Th> <Th> Mass (kg) </Th> <Th> Atomic percent </Th> <Th> Essential in humans </Th> <Th> Negative effects of excess </Th> <Th> Group </Th> </Tr>

The element which is the most abundant in the human body is