Roughly 96% of the mass of the human body is made up of the four elements which are carbon, oxygen, hydrogen and nitrogen.
The elements, oxygen and hydrogen are found predominantly in water, which makes up 60% of body's weight approximately. Element carbon is synonymous with life. The central role of the element, carbon is due to the fact that the carbon has 4 bonding sites which allow the element for the building of long and the complex chains of molecules. Nitrogen is found in the organic molecules, including the amino acids which make up proteins, and nucleic acids which make up DNA.
Compounds are substances made of at least 2 different elements. Molecules have at least 2 atoms, doesn't have to be different elements. Compounds and molecules both work.
