Question

The second ionization enthalpy of Mg is much lower than its first ionization enthalpy. Give reason.
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Answer 1

The electronic configuration of ₁₂Mg is -

1s² 2s² 2p⁶ 3s²

₁₂Mg  --------------------------> ₁₁Mg                                                  I.E₁

(stable)                       (1s² 2s² 2p⁶ 3s¹)  <---- less stable

₁₁Mg   -------------------------->₁₀Mg                                                 I.E₂

(less stable)               (1s² 2s² 2p⁶)  <----  stable

Here in the second ionization enthalpy we can see that Mg attains noble gas configuration hence stable. While in the first ionization enthalpy Mg turns less stable; comparative to the former I.E₂<< I.E₁.  

Answer 2

Answer:

The electronic configuration of ₁₂Mg is -

1s² 2s² 2p⁶ 3s²

₁₂Mg  --------------------------> ₁₁Mg                                                  I.E₁

(stable)                       (1s² 2s² 2p⁶ 3s¹)  <---- less stable

₁₁Mg   -------------------------->₁₀Mg                                                 I.E₂

(less stable)               (1s² 2s² 2p⁶)  <----  stable

Here in the second ionization enthalpy we can see that Mg attains noble gas configuration hence stable. While in the first ionization enthalpy Mg turns less stable; comparative to the former I.E₂<< I.E₁.