# In which of the following arrangements the order is NOT according to the property indicated against it? Option 1) $Al^{3+}- increasing ionic size Option 2) $B   - increasing first ionisation enthalpy Option 3) $I    increasing electron gain enthalpy    (with negative sign) Option 4) $Li  - increasing metallic radius

As we learnt in

Factors affecting I.E -

Removal of an electron from half filled and full filled atom require more energy than expected.

When we look into option 2, we find a discrepancy there that O is shown to have a greater I.E than N. Usually, I.E increases along a period but as N has half filled orbitals, removal of electrons requires more energy.

Option 1)

$Al^{3+}- increasing ionic size

This option is incorrect.

Option 2)

$B   - increasing first ionisation enthalpy

This option is correct.

Option 3)

$I    increasing electron gain enthalpy    (with negative sign)

This option is incorrect.

Option 4)

$Li  - increasing metallic radius

This option is incorrect.

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