Question

Calculate the number of 4f electrons present in \[{\rm{G}}{{\rm{d}}^{{\rm{2 + }}}}\] (Atomic number=64).

Answer 1

Hint: Electronic configuration of an element is the arrangement of electrons in the orbital in the order of increasing energy of the orbital. It is the most important factor for the determination of the valency of an element.

Complete Step by Step Solution:
The element, Gadolinium (Gd) has an atomic number of 64. So, its electronic configuration is,
\[[Xe]4{f^7}5{d^1}6{s^2}\]
We know, a cation has less number of electrons than the atom. The electronic configuration of cation of Gadolinium (Gd), that is, \[{\rm{G}}{{\rm{d}}^{{\rm{2 + }}}}\]is
\[[Xe]4{f^7}5{d^1}\]
Now, after the loss of two electrons, due to the contraction of orbitals, 5d electron will get transferred to 4f and the electronic configuration of \[{\rm{G}}{{\rm{d}}^{{\rm{2 + }}}}\]becomes \[[Xe]4{f^8}5{d^0}\].
Hence, the count of electrons in the 4f orbital of \[{\rm{G}}{{\rm{d}}^{{\rm{2 + }}}}\]ion is 8.

Additional information:
1) Lanthanide contraction defines the phenomenon of decreasing trend of the size of elements in the series of Lanthanide from Cerium to Lutetium. The reason for the lanthanide contraction is due to the poor shielding effects of 4f electrons.
2)Some of the elements of the Lanthanide series are Lanthanum, Cerium, Gadolinium etc.
3) Lanthanides possess lustre properties and appear silvery in colour. They are metals of soft nature and can easily be cut using a knife. They can undergo corrosion or become brittle in nature if they undergo contaminated with any non-metals or other metals

Note: Gadolinium is a metal of silvery-white colour. It has slightly malleability and ductility properties and it is a rare-earth element. The reaction of Gadolinium with atmospheric oxygen or moisture results in the formation of a black coating slowly. It is found naturally in the oxidised form.