In which of the following arrangements the order is NOT according to the property indicated against it?

  • Option 1)

    Al^{3+}<Mg^{2+}<Na^{+}<F^{-}- increasing ionic size

  • Option 2)

    B<C<N<O   - increasing first ionisation enthalpy

  • Option 3)

    I<Br<F<Cl    increasing electron gain enthalpy    (with negative sign)

  • Option 4)

    Li<Na<K<Rb  - increasing metallic radius

 

Answers (1)

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+}<Mg^{2+}<Na^{+}<F^{-}- increasing ionic size

This option is incorrect.

Option 2)

B<C<N<O   - increasing first ionisation enthalpy

This option is correct.

Option 3)

I<Br<F<Cl    increasing electron gain enthalpy    (with negative sign)

This option is incorrect.

Option 4)

Li<Na<K<Rb  - increasing metallic radius

This option is incorrect.

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