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

Question

In which of the following arrangements, the order is not according to the property indicated against it? (A) Al 3+< Mg 2+< Na +< F -: Increasing ionic size (B) B < C < N < O: Increasing first ionisation enthalpy (C) I< B r< F< C l: Increasing electron gain enthalpy with negative sign (D) Li < Na < K < Rb: Increasing metallic radius

Tardigrade Admin · Accepted Answer

(a) All of these are isoelectronic ions with decreasing nuclear charge and increasing ionic size.

A l^{3 +} (Z = 13) < M g^{2 +} (Z = 12) < N a^{+} (Z = 11) < F^{-} (Z = 9)

(b)

I E_{1}

of these elements are in the order:

B < C < O < N

I E_{1}

of

N (1 s^{2} 2 s^{2} 2 p^{3})

is more than

O (1 s^{2} 2 s^{2} 2 p^{4}),

due to

extra stable half filled

2 p

-subshell in the valence shell. Thus, the given order is not correct.

(c) Electron gain enthalpies of these elements are

I (- 295 k J m o l^{- 1}) < B r (- 325 k J m o l^{- 1}) < F (- 328 k J m o l^{- 1}) < Cl (- 349 k J m o l^{- 1)}

(d) Metallic radius increases down the group.

Q. In which of the following arrangements, the order is not according to the property indicated against it?

$A l^{3 +} < M g^{2 +} < N a^{+} < F^{-}$ : Increasing ionic size

$B < C < N < O$ : Increasing first ionisation enthalpy

$I < B r < F < Cl$ : Increasing electron gain enthalpy with negative sign

$L i < N a < K < R b$ : Increasing metallic radius

Q. In which of the following arrangements, the order is not according to the property indicated against it?

Al3+<Mg2+<Na+<F− : Increasing ionic size

B<C<N<O : Increasing first ionisation enthalpy

I<Br<F<Cl : Increasing electron gain enthalpy with negative sign

Li<Na<K<Rb : Increasing metallic radius

$A l^{3 +} < M g^{2 +} < N a^{+} < F^{-}$ : Increasing ionic size

$B < C < N < O$ : Increasing first ionisation enthalpy

$I < B r < F < Cl$ : Increasing electron gain enthalpy with negative sign

$L i < N a < K < R b$ : Increasing metallic radius