Q3 / 160 · TS EAMCET 2023 (14 May Shift 2) · Chemistry

Assertion (A): First ionisation enthalpy of oxygen is less than that of nitrogen Reason (R): Atoms with half-filled or completely filled orbitals are less stable The correct option among the following is

  • A
    (A) and (R) are true. (R) is the correct explanation of (A)
  • B
    (A) and (R) are true, but (R) is not correct explanation of (A)
  • Correct answer
    C
    (A) is true but (R) is false
  • D
    (A) is false but (R) is true

Solution

The first ionisation enthalpy of oxygen is less than that of nitrogen. This is due to the stability of halffilled electronic configuration. Nitrogen has half filled electronic configuration and hence its ionisation energy is greater than oxygen. In oxygen, after losing its electron, it goes to half filled electronic configuration and hence, it has less ionisation energy than litrogen.

Hence, the correct answer is option: 'C'.

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