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JEE Main 2025 Apr 4 Shift 2, Chemistry Q17: Group13 Elements: The Boron Family

JEE Main2025Apr 4, Shift 2Chemistry
Q.

The elements of Group 13 with highest and lowest first ionisation enthalpies are respectively:

  1. A

    B & Ga

  2. B

    B & Tl

  3. C

    Tl & B

  4. D

    B & In

Solution

The first ionisation enthalpies of group-13 elements do not decrease monotonically because of poor shielding by the intervening and electrons in Ga, In and Tl.

The observed order is:

Hence boron has the highest first ionisation enthalpy and indium has the lowest.

B & In.

Concept behind this question

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