Answer: Increasing cation size reduces lattice energy and increases hydration enthalpy advantage; larger M 2+ also holds OH- less tightly.
- A Increasing cation size reduces lattice energy and increases hydration enthalpy advantage; larger M<sup>2+</sup> also holds OH- less tightly
- B The atomic mass of each successive Group 2 metal supposedly decreases steadily down the group according to standard textbooks
- C The electronegativity of the metal supposedly increases steadily down the group toward fluorine-like values in general practice
- D The first ionisation energy of the metal supposedly increases steadily down the group instead of falling as frequently described
Correct answer: A. Increasing cation size reduces lattice energy and increases hydration enthalpy advantage; larger M<sup>2+</sup> also holds OH- less tightly
Explanation: From Mg(OH)<sub>2</sub> (sparingly soluble, weakly basic) to Ba(OH)<sub>2</sub> (soluble, strongly basic): larger, less polarising cations release OH- more freely and their hydroxides have lower lattice energies.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.