Ammonium sulphate has a molecular formula of (NH4)2SO4.

- Each unit of ammonium sulphate contains two ammonium ions (NH4+) and one sulphate ion (SO42-).

- Each ammonium ion consists of one nitrogen atom and four hydrogen atoms, so two ammonium ions contain 2 nitrogen atoms and 8 hydrogen atoms.

- Each sulphate ion consists of one sulphur atom and four oxygen atoms, so one sulphate ion contains 1 sulphur atom and 4 oxygen atoms.

Hence, one unit of ammonium sulphate contains 2 nitrogen atoms, 8 hydrogen atoms, 1 sulphur atom and 4 oxygen atoms.

In total, there are 20 atoms in one unit of ammonium sulphate.