How many atoms are in copper sulphate CuSO4?

Copper on the Periodic Table of Elements is Cu. Copper is 1 atom.

Sulphur on the Periodic Table of Elements is S. Sulphur is 1 atom.

Oxygen on the Periodic Table of Elements is O. Since there is a 4 next to the O, it's 4 atoms of Oxygen.

1 Atom of Copper + 1 Atom of Sulphate + 4 Atoms of Oxygen = 6 Atoms.