Atomic mass of Mg = 24
Atomic mass of S = 32
Ratio of Mg and S in Magnesium sulphide = 24:32 = 3:4
Mass ratio / Atomic mass of Magnesium (Mg) = 3 24 = 1 8
Mass ratio / Atomic mass of Sulphur (S) = 4/ 32 = 1/ 8
Hence, ratio of atoms in Magnesium sulphide (MgS) = 1/ 8 : 1 /8 or 1 : 1.