In chemistry, iron (TR:157) (LH:12) (TL:169), symbol Fe, the 26th element (Z:26) of the periodic table, is an atom, with a mass of 55.85 amu, comprised of 26 protons, 30 neutrons, and 26 electrons; with an electron configuration of: [Ar] 3d6 4s2.
The following is an early estimate of the percent iron in humans:
- “The human body contains carbon 13.5%, hydrogen 9.1%, oxygen 72%, nitrogen 2.5%, phosphorus 1.15%, sodium 0.1 %, calcium 1.3%, magnesium 0.001%, iron 0.01%, and traces of silicon and fluorine.”
- — Carl Kelsey (1916), The Physical Basis of Society (pg. 7) 
- Iron – Hmolpedia.