The first, second and third ionisation enthalpies of a metal M are 590 kJ mol ⁻¹ , 1145 kJ mol ⁻¹ and 4912 kJ mol ⁻¹ respectively. Elements X and Y have electron gain enthalpies of -348 kJ mol ⁻¹ and -295 kJ mol ⁻¹ respectively. Assuming X and Y are monovalent non-metals, what are the correct formulas for the compounds formed by M with X and Y, and the correct order of their ionic character?

Step-by-step solution

The successive ionisation enthalpies of metal M show a sudden, large jump between the second ( 1145 kJ mol ⁻¹ ) and third ( 4912 kJ mol ⁻¹ ) ionisation enthalpies. This indicates that M has two valence electrons and will form an M ²⁺ ion. Since X and Y are monovalent non-metals (forming X ⁻ and Y ⁻ ions), the formulas of the compounds formed will be MX ₂ and MY ₂ . The ionic character of a bond increases with the tendency of the non-metal to accept an electron, which corresponds to a more negative electron gain ent