Answer
In the reaction below:
Cu + HCI > CuCl2 + H2
hydrogen is written as "H2" and not "H"
Reason:
The main reason for this it is because Hydrogen only have one electron, meaning it is highly unstable. It needs another electrons to be stable. This is why it bonds with another hydrogen (with one electron) so that it can be stable. It exists as H2 rather than H. Atomic hydrogen is highly unstable and Do not exist in normal conditions.
