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Class 11
Chemistry
Classification of Elements and Periodicity in Properties
how would you explain the fact that the first ioni...

Question:
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 2^nd member of group I (alkali metals) & magnesium is the 2^nd member of group II (alkaline earth metals). The first ionization enthalpy of sodium is more than that of magnesium. This is primarily because of smaller size & more symmetrical electronic configuration.For these reasons, the energy required to remove an electron from magnesium is more than the energy required in sodium. Hence, the first ionization enthalpy of sodium is lower than that of magnesium.

However, the second ionization enthalpy of sodium is higher than that of magnesium. This is because after losing 1 electron, sodium attains the stable noble gas configuration of neon (1s²2s²2p⁶) . On the other hand, magnesium, after losing 1 electron still has one electron in the 3s-orbital(1s² 2s²2p⁶3s¹). In order to attain the stable noble gas configuration, it still has to lose one more electron. Thus, the energy required to remove the second electron in case of sodium is much higher than that required in case of magnesium. Hence, the second ionization enthalpy of sodium is higher than that of magnesium.

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Question:
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?

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Question: 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?

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Question:
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?