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JEE Main 2026 Apr 6 Shift 2, Chemistry Q8: Periodicity In Atomic Properties

JEE Main2026Apr 6, Shift 2Chemistry
Q.

In a period, the first ionisation enthalpy of the element at extreme left and the negative electron gain enthalpy of the extreme right element, except noble gases, are respectively.

  1. A

    lowest and lowest

  2. B

    highest and lowest

  3. C

    lowest and highest

  4. D

    highest and highest

Solution

The leftmost element in a period is a group-1 alkali metal: across a period its first ionisation enthalpy is the lowest (one loosely held outer electron).

The rightmost element (excluding noble gases) is a group-17 halogen: its electron gain enthalpy is the most negative (i.e., largest in magnitude) because gaining one electron completes the octet.

Concept behind this question

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