Alongside oxygen and hydrogen, what is the other element that accounts for the vast majority of living matter?

In living organisms the most abundant elements are carbon, hydrogen, and oxygen. These three elements along with nitrogen, phosphorus, and a handful of other elements account for the vast majority of living matter. An atom is one single unit of a chemical element.

All matter, whether it is living or not, is composed of chemical elements; these are fundamental chemicals in the sense that they are what they are - they can't be changed into another element. Each element is distinguished by the number of protonstext annotation indicator, neutronstext annotation indicator, and electronstext annotation indicatorthat it possess. For example, carbon's atomic number is 6, and has an atomic mass of about 12, because it has 6 positively charged protons and 6 non-charged neutrons. The 6 charged electrons contribute very little to the atomic mass. There are 92 naturally-occurring elements on earth.