The human body contains many elements from the periodic table. It is mostly composed of oxygen and carbon, but trace elements also have a significant role. The table gives the mass, in kilograms, of some elements found in the human body, based on a 70.0kg person. Carbon makes up what fraction of the mass of the human body? Give your answer in decimal form. fraction of C Carbon makes up what percentage of the mass of the human body? What is the mass of phosphorus in a 33kg person