Question

Define lanthanoid contraction.

Hint:

Lanthanoid contraction explains the similarity in properties of elements like zirconium and hafnium.

Answer 1

Step 1: In lanthanoids, electrons are added to the 4f-orbitals.
Step 2: The 4f-electrons have poor shielding effect compared to s and p electrons.
Step 3: As a result, the effective nuclear charge experienced by the outer electrons increases gradually.
Step 4: This increased attraction causes a decrease in atomic and ionic sizes, known as lanthanoid contraction.