# In which of the following options the order of arrangement does not agree with the variation of property indicated against it? Option 1) Al3+ > Mg2+ < Na+ < F- (increasing ionic size) Option 2) B < C < N < O (increasing first ionisation enthalpy) Option 3) I < Br < Cl < F (increasing electron gain enthalpy Option 4) Li < Na < K < Rb (increasing metallic radius)

Electron gain enthalpy -

When an electron is added to a neutral gaseous atom (x) to convert it into a negative ion, the enthalpy change accompanying the process is defined as the electron gain enthalpy
$(\Delta_{eg}H^\circleddash )$

-

Ionization enthalpy -

It is defined as the minimum amount of energy required to remove the outer most shell electron from an isolated gaseous atom (X) to form the gaseous ion.

- wherein

$X_{(g)}\rightarrow X^{+}_{(g)}$  $+e^{-}$

The correct order of increasing  negative electron gain ethaepy is I < Bo<F<cl and the correct order of increasing first ionisation ethalpy is B<C<O<N

Option 1)

Al3+ > Mg2+ < Na+ < F- (increasing ionic size)

This option is incorrect

Option 2)

B < C < N < O (increasing first ionisation enthalpy)

This option is incorrect

Option 3)

I < Br < Cl < F (increasing electron gain enthalpy

This option is correct

Option 4)

Li < Na < K < Rb (increasing metallic radius)

This option is incorrect

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