Nitric acid is HNO3 while Calcium Hydroxide is a base with a chemical formula Ca(OH)2. When acid reacts with base, it forms salt and water (H20). Hence forming the equation HNO3 + Ca(OH)2 -> Ca(NO3)2 + H20.
To gain the same number of atoms on both sides, the balanced molecular equation should be:
2NO3 + Ca(OH)2 -> Ca(NO3)2 + 2H2O
with: 4 Hydrogen, 2 Nitrogen, 8 Oxygen, and 1 Calcium