An ionic chloride of a metal, R, has the formula RCl3\mathrm{RCl_3}RCl3. The chloride ion is Cl−\mathrm{Cl^-}Cl−.
The R ions have the same charge in the chloride and the sulfide. A student writes R3S2\mathrm{R_3S_2}R3S2 as the formula for the sulfide of R. The sulfide ion is S2−\mathrm{S^{2-}}S2−.
Explain, using ionic charges, why the student's formula is incorrect and give the correct formula for the sulfide of R.
119 exam-style questions on Edexcel GCSE Chemistry 2.3 Ionic bonding, covering 2.3.1 Ions and the formation of ionic bonds, 2.3.2 Naming and deducing formulae of ionic compounds, and 2.3.3 Giant ionic lattices. Each one has a worked solution and a mark scheme showing where the marks go.