What is
lanthanoid contraction? What are the consequences of lanthanoid
contraction?
What is lanthanoid contraction? What are the consequences of lanthanoid
contraction?
As
we move along the lanthanoid series, the atomic number increases
gradually by one. 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 interelectronic repulsions due to the addition of
electron. Also, with the increase in atomic number, the number of
electrons in the 4f
orbital also increases. The 4f
electrons have poor shielding effect. Therefore, the effective
nuclear charge experienced by the outer electrons increases.
Consequently, the attraction of the nucleus for the outermost
electrons increases. This results in a steady decrease in the size of
lanthanoids with the increase in the atomic number. This is termed as
lanthanoid contraction.
Consequences
of lanthanoid contraction
(i) There
is similarity in the properties of second and third transition
series.
Separation
of lanthanoids is possible due to lanthanide contraction.
(iii) It is due
to lanthanide contraction that there is variation in the basic
strength of lanthanide hydroxides. (Basic strength decreases from
La(OH)3
to Lu(OH)3.)
As we move along the lanthanoid series, the atomic number increases gradually by one. 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 interelectronic repulsions due to the addition of electron. Also, with the increase in atomic number, the number of electrons in the 4f orbital also increases. The 4f electrons have poor shielding effect. Therefore, the effective nuclear charge experienced by the outer electrons increases. Consequently, the attraction of the nucleus for the outermost electrons increases. This results in a steady decrease in the size of lanthanoids with the increase in the atomic number. This is termed as lanthanoid contraction.
Consequences of lanthanoid contraction
(i) There is similarity in the properties of second and third transition series.
Separation of lanthanoids is possible due to lanthanide contraction.
(iii) It is due to lanthanide contraction that there is variation in the basic strength of lanthanide hydroxides. (Basic strength decreases from La(OH)3 to Lu(OH)3.)
