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The living species comprise more number of hydrogen atoms in comparison to any other atoms, still 65 percent of the usual organism's mass is oxygen. The prime reason for this is that an atom of oxygen comprises sixteen times more mass in comparison to a hydrogen atom.  

Hydrogen possesses only one proton and no neutrons, and therefore, the atomic number of hydrogen is one and its mass is one. On the other hand, oxygen has eight protons and eight neutrons, and therefore, the atomic number of oxygen is 8 and its mass is 16. Hence, it will take 16 hydrogen atoms to equal the mass of one oxygen atom.  

Explanation: 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.

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