Question

What is lanthanide contraction State the cause and two consequences of lanthanide contraction.

Answer 1

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❤.LANTHANIDE CONTRACTION :

The gradual decrease of atomic size from left to right in lanthanides is called "lanthanide contraction".

❤.CONSEQUENCE:

The crystal structure and other properties of these elements become very close and similar.So it become difficult to separate them from a mixture.

Inert pair effect is consequence of Lanthanide contraction.

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Answer 2

Question :

What is lanthanide contraction. State the cause and two consequences of lanthanide contraction.

Class : 11

Chapter : Periodic Classification of Elements

Topic : Atomic Radius

Answer :

In the lanthanide series of elements, the differentiating electron enters into the 4f-orbital of the antepenultimate shell. The general electronic configuration of lanthanides is 4f¹⁻¹⁴ 5d⁰⁻¹ 6s². The new electron of each element is not entering into the outermost shell. Moreover for every electron added outside the nucleus, a proton is added in the nucleus. The nuclear charge increases. Its ability to attract the outer electron increases, causing a decrease in the atomic size steadily. Among the lanthanides Eu and Yb have highest and second highest atomic radii due to the difference in their crystal lattice structures.

The decrease in the size of lanthanides and their trivalent ions is described as lanthanide contraction. The contraction in size from one element to the next element in the lanthanide series is fairly small. But commutative effect over 14 lanthanide elements is about 0.2A⁰. This is a significant decrease in size and is known as lanthanide contraction.

Consequences of lanthanide contraction:

Due to their peculiar shape, f-orbitals do not provide effective screening for the outer electrons from the nuclear attraction. This may be the reason for the lanthanide contraction. The increase in the size of an atom from a 4d-element to a 5d-element is less significant. This is attributed to Lanthanide contraction.

Hardness, melting and boiling point of elements increase from Ce to Lu due to lanthanide contraction. It is also difficult to separate lanthanides  even by techniques like chromatography. Because of the lanthanide contraction, the elements, the elements of third transition series have smaller radii than would otherwise be anticipated.

As the size of the lanthanide ions decreases from Le⁺³ to Lu⁺₃, the covalent character of M-OH bond increases and hence the basic strength decreases from Ce(OH)₃. Actinium to lawrencium are the elements of actinide series. The radii of these elements decrease regularly along the series because the extra charge on the nucleus is poorly shielded by 5-f electrons. This results in actinide contraction, similar to lanthanide contraction.

For information on Atomic Radius do refer to : https://brainly.in/question/23403133

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