To determine the number of atoms in 3Cu(NO3)2, we need to multiply the number of atoms of each element by the respective coefficients in the chemical formula and then sum them up.

In 3Cu(NO3)2, we have:

- 3 copper (Cu) atoms

- 6 nitrogen (N) atoms

- 18 oxygen (O) atoms

So, the total number of atoms in 3Cu(NO3)2 is:

3 Cu atoms + 6 N atoms + 18 O atoms = 27 atoms

Therefore, there are 27 atoms in 3Cu(NO3)2.