The statement is absolutely true. H differs from 2H.
Justification:
- H represents a single atom of hydrogen. Basically hydrogen cannot exist as a single atom. It is diatomic.
- 2H represents 2 atoms of hydrogen.
- Mass of H atom = 1 u
- Mass of 2H atom = 2 × 1 u = 2u
Hope you could get an idea from here.
Doubt clarification - use comment section.
