Heptatomic molecules contain 7 atoms: No. of H atoms = 2 No. of S atoms = 1 No. of O atoms = 7 - 2 - 1 = 4 The formula is thus H2SO4 (sulfuric acid) Solution Heptatomic molecules contain 7 atoms: No. of H atoms = 2 No. of S atoms = 1 No. of O atoms = 7 - 2 - 1 = 4 The formula is thus H2SO4 (sulfuric acid).