Question

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

Answer 1

Answer:

Explanation:

The first ionization enthalpy of sodium is lower than of magnesium because of smaller size and more symmetrical electronic configuration. Thus, the energy required to remove an electron from magnesium is more than the energy required in sodium.

However, the second ionization enthalpy of sodium is higher than that of magnesium because after losing one electron, sodium attains the stable noble gas configuration of neon is 1s2 ,2s2 , 2p6. On the other hand magnesium, after losing one electron it attains the stable noble gas configuration is 1s2, 2s2 2p6, 3s1 . It means it has to lose one more election. Thus, the energy required to remove an electron from sodium is more than that of magnesium.