In chemistry, fluorine (LH:12), symbol F, the 9th element (Z:9) of the periodic table, is an atom, with a mass of 19 amu, comprised of 9 protons, 10 neutrons, and 9 electrons; with an electron configuration of: [He] 2s2 2p5.
The following is an early estimate of the percent fluorine 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) 
- Fluorine – Wikipedia.