This is the balanced chemical equation for the reaction between nitric acid $HNO3$ and copper $Cu$ to produce copper$II$ nitrate $Cu(NO3)2$, nitrogen dioxide $NO2$, and water $H2O$:

3HNO3 + 8Cu -> 3Cu$NO3$2 + 2NO2 + 4H2O

The reaction is balanced with 3 moles of nitric acid reacting with 8 moles of copper to produce 3 moles of copper$II$ nitrate, 2 moles of nitrogen dioxide, and 4 moles of water.