Question

what is lanthanide contraction?How would you account for it? What are its important consequences.

Answer 1

The decrease in size of lanthanide ion due to increase in atomic number is known as lanthanide contraction. Consequences of lanthanide contraction:

• Hard to separate the lanthanides

• Increase in electronegativity

• Increase in ionisation energy

• Ability of complex formation decreases

With an increase in the atomic number, the positive charge on nucleus increases by one unit and one more electron enters same 4f subshell.

The electrons in 4f subshell imperfectly shield each other. Shielding in a 4f subshell is lesser than in d subshell.

With the increase in nuclear charge, the valence shell is pulled slightly towards the nucleus. This causes lanthanide contraction.