Answer:
5 atoms
Step-by-step explanation:
When a chemical reaction starts with 5 atoms of hydrogen, and the reaction goes into completion, it must give us 5 atoms of hydrogen.
This is in compliance with the law of conservation of mass which states that "in a chemical reaction, matter is neither created nor destroyed but converted from one form to another".
In chemical reactions, bonds are broken and new compounds are formed in the process. The same number of species at the start and end of the reaction must still be the same.