The first four successive ionization enthalpies (in kJ mol ⁻¹ ) for two unidentified Period 3 elements, X and Y, are given below: Element X: 737, 1450, 7730, 10500 Element Y: 577, 1816, 2744, 11577 Identify the groups to which X and Y belong, and choose the correct relationship between their first ionization enthalpies ( _ i H₁ ).

Step-by-step solution

Analyze the successive ionization enthalpies to find the number of valence electrons: For element X, there is a sudden large jump between the second ( 1450 kJ mol ⁻¹ ) and third ( 7730 kJ mol ⁻¹ ) ionization enthalpies. This indicates that X has 2 valence electrons, so it belongs to Group 2 (Magnesium). For element Y, the large jump occurs between the third ( 2744 kJ mol ⁻¹ ) and fourth ( 11577 kJ mol ⁻¹ ) ionization enthalpies. This indicates that Y has 3 valence electrons, so it belongs to Group 13 (Aluminium). C