How are these two elements different ? hydrogen and oxygen- which one has the greatest mass ?

Explanation:

Hydrogen and Oxygen have many properties in common, but they have a lot of differences as well. Both are gases, both are colorless, both are odorless. They both differ from each other in the following regard:

Hydrogen has one unpaired electron whereas oxygen has two unpaired electrons.

Hydrogen can form only one covalent bond whereas oxygen can form two covalent bonds.

The most common isotope in hydrogen has no neutron in its nucleus whereas there are 8 neutrons in most common isotope of oxygen.

Atomic mass of oxygen is far greater than that of hydrogen. Hydrogen has an atomic mass of 1.00794u where as oxygen has an atomic mass of 15.999u