MgO (s) + 2HNO3 (aq) ----> Mg(NO3)2 (aq) + H2O (l)
This is a neutralisation reaction, and hence, acid + base ----> salt + water, where MgO is a base (metallic oxides are generally bases) and HNO3 is an acid.
In regards to your question, the hydrogen is covalently bonded to oxygen to form...