Question

How many unpaired electrons are present in\[N{i^{2 + }}\]:
A) 1
B) 2
C) 3
D) 4

Answer 1

Hint: An unmatched or unpaired electron refers to a single electron that is found inside an orbital. Each infinitesimal orbital of an energy level has a capacity to contain at most two electrons with contrary/opposite spins.

Complete Step by Step Solution:
According to Afbau’s principle, the electrons are needed to be arranged according to the increasing energy of the subshells.
The increasing order of subshells based on their energy is:-
1s< 2s <2p< 3s <3p <4s <3d< 4p <5s< 4d <5p <6s< 4f< 5d <6p<7s<5f<6d<7p
Electronic configuration of Nickel (Ni), which has an atomic number of 28 is,
\[Ni{\text{ }}\left( {Z{\text{ }} = {\text{ }}28} \right){\text{ }} = \;1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^8}\]
Electronic configuration of \[N{i^{2 + }}\] which has two electrons less in number than its neutral state is,
\[Ni{\text{ }}\left( {Z{\text{ }} = {\text{ }}26} \right){\text{ }} = \;1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^0}3{d^8}\]
There are 2 number of unpaired electrons in \[N{i^{2 + }}\].
As it is clearly observable from the above electronic configuration, Nickel at its neutral state has 8 electrons in its 3d energy level, i.e 3 orbitals are fully filled with paired electrons and two electrons lie unpaired. In \[N{i^{2 + }}\], the same electronic configuration is there with 2 electrons lost from the 4s sub-shell. Hence two unpaired electrons remain exactly the same.
Hence, the correct answer is, option (B).

Note: Atomic orbital is a mathematical function, it provides insight into the wave nature of electrons that exists around the nuclei of atoms. These mathematical functions are often used in order to determine the probability of finding an electron in a specific region around the nucleus of the atom. While filling up orbitals with electrons, one should always remember to fill up the orbitals according to their energy levels. Before pairing up electrons in an orbital, all the orbitals must have at least one electron. An unmatched electron has a glamorous dipole moment, while an electron brace has no dipole moment because the two electrons have contrary spins so their glamorous dipole fields are in contrary directions and cancel. Therefore a snippet with unmatched electrons acts as a glamorous dipole and interacts with a glamorous field.