Name: Lanthanoid Contraction
Uploaded: 2019-07-19
Duration: 4 min 23 s
Description: The steady decrease in atomic and ionic sizes of lanthanide elements with increasing atomic number is called lanthanoid contraction. It affects certain prope...

Question

What is lanthanide contraction? What are its cause and consequences?

Accepted Answer

Lanthanide contraction- The decrease in size of lanthanide ion due to increase in atomic number is known as lanthanide contraction. This is also due to the poor shielding effect of the electrons which present in the inner f orbital.

Cause of Contraction:- As we move along in the lanthanide series, the atomic number increases gradually by one. The number of electrons in the 4f orbital also increases.The 4f electrons have poor shielding effect. This means that the number of electrons and protons present in an atom also increases by one. As electrons are being added to the same shell, the effective nuclear charge increases. This happens because the increase in nuclear attraction due to the addition of proton is more pronounced than the increase in the inter-electronic repulsions due to the addition of electron in the same sub-shell.

Consequences of lanthanide contraction :-

(i) There will be similarity in the properties of second and third transition series such as the atomic size of Hafnium and Zirconium are almost same.

(ii) Separation of lanthanide is possible but it takes more time due to lanthanide contraction.

What is lanthanide contraction? What are its cause and consequences?

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