In the box provided explain why living organisms contain more hydrogen atoms than any other atoms, yet 65% of a typical organism's mass is oxygen.

The reason is that Oxygen atoms contain 16 times more mass than Hydrogen atoms.

Explanation:

Hydrogen H 11 Has only one proton and no neutrons and so has an atomic number of 1 and a mass of 1

Oxygen O 168 Has 8 protons and also 8 neutrons and having atomic number of 8 and a mass of 16.

Hydrogen takes 16 Hydrogen atoms to equal the mass of 1 oxygen atom.