"<span>Let's start with the basics: you have
probably heard that your body is 90% (or 85% or 95%) water. In actual
fact, water is (probably--unless you are obese) the majority of your
body weight--but nowhere near 90%. The best estimate I have seen is 57%
(Body water). So that puts hydrogen and oxygen in the top four.
As
I mentioned, extremely obese people can be less than 50% water. Fat
(triglycerides) is composed of carbon, hydrogen, and oxygen. The
majority of the mass of a triglyceride is carbon--chemically it is
closely related to biodiesel. So that puts carbon in the top four.
Finally,
amino acids which make up proteins (which make up muscle) require
nitrogen. That makes the top four.: Oxygen, Carbon, Hydrogen, and
Nitrogen.
But wait! What about bones? Aren't they calcium and phosphorous? Bones are really heavy.
It
turns out that calcium and phosphorous are indeed the next two most
abundant (by mass) elements in the body, but where nitrogen is about 3%
of your body mass, calcium and phosphorous are 1.5% and 1.2%
respectively.
You can find the full breakdown of the elemental composition of your body here: <span>Abundance of the chemical elements"
You must first calculate the total weight of 1 mole of the substance. You do this by finding the molar weights on the periodic table of each of the elements in the compound:
So now we take the amount of each element that is given in the compound and divide it by the total mass of the compound:
