alleryWhich Group-1 element has the LOWEST melting point and highest reactivity?
ALithium
BSodium
CPotassium
DCaesium
Answer & Solution
Correct answer: D. Caesium
1. Down Group 1, atomic size grows and metallic bonding weakens.
2. Weaker metallic bonds lower the melting point of the metal.
3. Larger atoms also lose their single valence electron more easily.
4. So reactivity rises down the group.
5. Caesium sits at the bottom of Group 1 of the four shown.
6. Hence caesium has the lowest melting point and highest reactivity.
_Source: Selina Concise Chemistry ICSE Class 10, Ch 1 'Periodic Table' (aplustopper.com extract)_
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