class wikitable sortable style text align center Atomic number Element Percent of MassThomas J Glover comp Pocket Ref 3rd ed Littleton Sequoia 2003 p 324 which in turn cites Geigy Scientific Tables Ciba Geigy Limited Basel Switzerland 1984 Distribution of elements in the human body by weight Retrieved on 2007 12 06 Mass kg J Emsley The Element 3rd ed Oxford Clarendon Press 1998 Atomic percent Positive health role in mammalsNeilsen cited Group 8 Oxygen 65 43 24 Yes water electron acceptor No Reactive Oxygen Species 16 6 Carbon 18 16 12 Yes organic compounds are hydrocarbon derivatives 14 1 Hydrogen 10 7 63 Yes e g water 1 7 Nitrogen 3 1 8 0 58 Yes e g DNA and amino acids 15 20 Calcium 1 4 1 0 0 24 Yes e g Calmodulin and Hydroxylapatite in bones 2 15 Phosphorus 1 1 0 78 0 14 Yes e g DNA and phosphorylation 15 19 Potassium 0 25 0 14 0 033 Yes e g Na K ATPase 1 16 Sulfur 0 25 0 14 0 038 Yes e g Cysteine and Methionine 16 11 Sodium 0 15 0 10 0 037 Yes e g Na K ATPase 1 17 Chlorine 0 15 0 095 0 024 Yes e g Cl transporting ATPase 17 12 Magnesium 0 05 0 019 0 0070 Yes e g binding to ATP and other nucleotides 2 26 Iron 0 006 0 0042 0 00067 Yes e g Hemoglobin 8 9 Fluorine 0 0037 0 0026 0 0012 Yes No topically hardens teeth toxic in higher amounts 17 30 Zinc 0 0032 0 0023 0 00031 Yes e g Zinc finger proteins 12 14 Silicon 0 002 0 0010 0 0058 Yes probable 14 37 Rubidium 0 00046 0 00068 0 000033 No 1 38 Strontium 0 00046 0 00032 0 000033 No 2 35 Bromine 0 00029 0 00026 0 000030 No 17 82 Lead 0 00017 0 00012 0 0000045 No toxic in higher amounts 14 29 Copper 0 0001 0 000072 0 0000104 Yes e g copper proteins 11 13 Aluminium 0 000087 0 000060 0 000015 No toxic 13 48 Cadmium 0 000072 0 000050 0 0000045 No toxic in higher amounts 12 58 Cerium 0 000057 0 000040 No 56 Barium 0 000031 0 000022 0 0000012 No toxic 2 50 Tin 0 000024 0 000020 6 0e 7 No 14 53 Iodine 0 000016 0 000020 7 5e 7 Yes e g thyroxine 17 22 Titanium 0 000013 0 000020 No 4 5 Boron 0 000069 0 000018 0 0000030 Yes probable 13 34 Selenium 0 000019 0 000015 4 5e 8 Yes No toxic in higher amounts 16 28 Nickel 0 000014 0 000015 0 0000015 Yes e g urease 10 24 Chromium