O Levels Chemistry (5070)•5070/12/M/J/21
Explanation
Group 1 alkali metal trends Steps:
- Caesium is below lithium in Group 1, so apply down-group trends.
- Melting points decrease due to increasing atomic size weakening metallic bonds.
- Reactivity with water increases as ionization energy decreases, easing electron loss.
- All Group 1 elements have one valence electron in the s orbital.
Why D is correct:
- D states lower melting point, more vigorous reaction, and same valence electrons, aligning with Group 1 trends where metallic bonding weakens, reactivity rises (lower IE), and ns¹ configuration holds.
Why the others are wrong:
- A: Melting point is lower, not higher.
- B: Reaction is more vigorous, not less; valence electrons same, not greater.
- C: Melting point lower and reaction more vigorous, not higher/less.
Final answer: D
Topic: Group I properties
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