Assertion A: The first ionization enthalpy for oxygen is lower than that of nitrogen.

Reason R: The four electrons in 2p orbitals of oxygen experience more electron-electron repulsion.

Question

Assertion A: The first ionization enthalpy for oxygen is lower than that of nitrogen.

Reason R: The four electrons in 2p orbitals of oxygen experience more electron-electron repulsion.

Canvas Classes · Accepted Answer

Strategy:
 Ionization enthalpy is affected by subshell stability. Half-filled () configurations have extra stability, while  configurations suffer from pairing repulsion.

Step 1: Evaluate Assertion (A)
- Nitrogen ():  (Half-filled).
- Oxygen ():  (One paired -orbital).
- Oxygen's  () is lower than Nitrogen's (). (True)

Step 2: Evaluate Reason (R)
- In Oxygen, the fourth -electron enters an orbital already occupied by another electron.
- This creates inter-electronic repulsion, which makes the

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