Answer: Be > Mg > Ca > Sr > Ba (decreases down the group as metallic bonding weakens).
- A Be > Mg > Ca > Sr > Ba (decreases down the group as metallic bonding weakens)
- B Ba > Sr > Ca > Mg > Be, increasing steadily down the group as frequently observed in practice
- C All five Group 2 metals show essentially identical hardness in many documented cases
- D Hardness is determined mainly by ambient temperature, not atomic size according to conventional understanding
Correct answer: A. Be > Mg > Ca > Sr > Ba (decreases down the group as metallic bonding weakens)
Explanation: Down Group 2, metal-metal bonds weaken (fewer valence electrons relative to increasing atomic size), reducing hardness.
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.