The gradual decrease in size across lanthanides due to poor shielding by 4f electrons.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
Lanthanide contraction is the steady decrease in atomic and ionic radii across the lanthanide series from lanthanum to lutetium. It occurs because each added 4f electron shields the nucleus poorly, so the effective nuclear charge rises steadily. As a result, the 5d elements have radii similar to those of the 4d elements above them in the table. This makes elements such as zirconium and hafnium chemically very similar, which makes them hard to separate. The effect is important in the chemistry of the rare earth metals.
Key ideas: Steady decrease in size from La3+ (103 pm) to Lu3+ (86 pm), due to poor shielding by 4f electrons as Z rises by 14. Result: 4d and 5d elements have almost identical radii (Zr 160 pm, Hf 159 pm), so Zr and Hf and Nb and Ta behave alike chemically and are hard to separate. It also raises IE of 5d metals, giving noble gold and platinum.
Common mistakes and connections: Students think the contraction occurs only in lanthanides; its effects continue through the 5d series and into p block (Tl, Pb). Another error is crediting it to nuclear charge alone: it is poor shielding. It explains the density of Hf, W, Os and Pt, and the inert pair effect.
Ln3+ radius falls steadily from 103 pm for La to 86 pm for Lu because poorly shielding 4f electrons let the nuclear charge pull the shell in. The interactive lesson shows this as a live animation or chart.
Zirconium and hafnium have almost identical atomic radii, about 160 pm and 159 pm respectively, which makes them very hard to separate.
The gradual decrease in size across lanthanides due to poor shielding by 4f electrons.
Lanthanide Contraction is a advanced topic in Atomic Structure & Periodicity. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Atomic Structure & Periodicity first: Metallic Character, Diagonal Relationship, Inert Pair Effect.
The next topics in Atomic Structure & Periodicity are Periodic Trends in Oxidation State and Periodic Trends in Oxides.
Yes. The interactive lesson includes a self-check question on Lanthanide Contraction, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Lanthanide Contraction is topic 96 of 115 in Atomic Structure & Periodicity.