Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :
- Statement I is true but Statement II is false
- Both Statement I and Statement II are true
- Statement I is false but Statement II is true
- Both Statement I and Statement II are false
Answer
(3) Statement I is false but Statement II is true
Solution
Statement I: Atomic radius decreases across a period: Mg (160 pm) > Al (143 pm).
For isoelectronic cations, higher charge gives smaller size: Mg2+ (72 pm) > Al3+ (53.5 pm).
Correct order: Mg > Al > Mg2+ > Al3+. Statement I is false.
Statement II: egH ( kJ mol-1): Cl = −349, Br = −325, S = −200, O = −141
O and F (period 2) are small, so the added electron suffers strong repulsion; hence S is more negative than O and Cl more negative than F.
Magnitude: Cl > Br > S > O. Statement II is true.
Answer: (3)