Q. 174.4( 21 Votes )

How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

Answer :

Sodium is the 2nd member of group I [alkali metals] & magnesium is the 2nd member of group II [alkaline earth metals]

The first ionization enthalpy of sodium is lower as compared to that of magnesium. This is because of smaller size and more symmetrical electronic configuration. This is the reason why the first ionization enthalpy of sodium is lower as compared to that of magnesium. However, the second ionization enthalpy of sodium is higher than that of magnesium. The simple reason is that after losing one electron sodium attains the noble gas configuration and thus energy required to remove the electron from the stable noble gas configuration of sodium is very much higher than that actually required to remove the second electron from magnesium atom.


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