Essential Elements

Most of the mass of the human body is made up of just 6 elements:

• 65% oxygen
• 18.5% carbon
• 9.5% hydrogen
• 3.2% nitrogen
• 1.5% calcium
• 1% phosphorus

Carbon and hydrogen are the building blocks making up organic (carbon) molecules, and so, since the human body is just an incredibly complicated organic chemical factory, it is no surprise that carbon and hydrogen make up such a huge amount of the mass of a human body. Oxygen is present in most of the biochemicals making up your body, while nitrogen is an essential component of proteins. Why is there so much phosphorus? Phosphorus and oxygen combine to make up the glue that holds your DNA together, no phosphorus, no DNA, no you! And calcium is ofcourse present in bones and teeth.
Then there are minor amounts of other elements such as potassium, sulfur, sodium, chlorine and magnesium which make up less than 1% of the remaining mass of the human body.

Some elements, like iron, are absolutely essential in order for the human body to survive, but are present in extremely minute amounts, for iron this is about 0.006%

H																		He
Li	Be												B	C	N	O	F	Ne
Na	Mg												Al	Si	P	S	Cl	Ar
K	Ca		Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
Rb	Sr		Y	Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
Cs	Ba	*	Lu	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
Fr	Ra	**	Lr	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Uut	Fl	Uup	Lv	Uus	Uuo
		*	La	Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb
		**	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No

Vanderbilt University Scientists have just found out that bromine is also essential.It appears that bromine is important to an enzyme that is used to make a particular type of sulfur-nitrogen bond within the collagen IV structure used to make the scaffold for cells.

Reference:
A. Scott McCall, Christopher F. Cummings, Gautam Bhave, Roberto Vanacore, Andrea Page-McCaw, Billy G. Hudson. Bromine Is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture. Cell, 2014; 157 (6): 1380 DOI: 10.1016/j.cell.2014.05.009

Further Reading
Periodic Table
Metals and Non-metals

Percentage Composition
Mass-Mole Calculations 

Suggested Study Questions:

1.  Give the chemical symbol for each of the following elements:
   • oxygen
   • carbon
   • hydrogen
   • nitrogen
2. Give the name for each of the following elements:
   • Fe
   • Ca
   • P
   • K
   • Mg
3. Give the atomic number for each of the following elements
   • sulfur
   • sodium
   • iodine
   • Cl
   • F
   • Br
4. Make a table of the metals and non-metals named in the article above
5. Chris the Chemist has a mass of 90 kg. Calculate the mass, in kilograms, of each of the following elements in Chris' body
   • carbon
   • hydrogen
   • oxygen
   • nitrogen
6. Calculate the mass of iron in Chris' body in
   • kilograms
   • grams
   • milligrams
   • micrograms
7. Calculate the moles of each of the following elements found in Chris' body
   • carbon
   • hydrogen
   • oxygen
   • nitrogen
8. Do you think Scientists will one day claim that lead is an element essential for human life? Explain your answer.