Group 2 element trends down the periodic table

Steps:

• Recall that atomic size increases from Mg to Ba, weakening metallic bonding and reducing ionisation energy.
• Note reactivity of Group 2 metals increases down the group, enhancing reducing power and decreasing oxidising power.
• Observe solubility trends: hydroxides become more soluble due to lower charge density of larger cations, while sulfates become less soluble.
• Identify the increasing property by comparing trends: only hydroxide solubility rises from Mg (low) to Ba (high).

Why C is correct:

• Solubility of Group 2 hydroxides increases down the group as lattice energy decreases more than hydration energy, per Fajans' rules on ionic character.

Why the others are wrong:

• A: First ionisation energy decreases due to increasing atomic radius and shielding.
• B: Oxidising power decreases as metallic reactivity strengthens down the group.
• D: Solubility of sulfates decreases due to reduced hydration energy outweighing lattice energy drop.

Final answer: C