Question

The ground state electronic configuration of the CO molecule is:
A. $1{\sigma ^2}2{\sigma ^2}1{\pi ^4}3{\sigma ^2}$
B. $1{\sigma ^2}2{\sigma ^2}3{\sigma ^2}1{\pi ^2}2{\pi ^2}$
C. $1{\sigma ^2}2{\sigma ^2}1{\pi ^2}3{\sigma ^2}2{\pi ^2}$
D. $1{\sigma ^2}1{\pi ^4}2{\sigma ^2}3{\sigma ^2}$

Answer 1

According to Dalton’s theory the atom is the most basic form of matter but the atom contains various subatomic particles like the electrons and protons. The atomic structure of the atom depends on the electronic configuration in which the electrons are arranged inside the atoms. This electronic configuration is responsible for various properties that the atom shows. The molecular orbital theory uses the formation of molecular orbitals rather than electronic orbitals of individual elements.

Complete step by step answer:
The earlier theories of the arrangement of the electrons suggested the existence of the shells and revolving electrons but later the molecular orbital theory came and put forward a new idea of molecular orbitals, disregarding the previous arrangements and theories.
In this question, we have to find the ground state electronic configuration of $CO$ molecule. $CO$ Molecule is composed of two atoms of different elements. Such molecules are called heteroatomic molecules. In heteroatomic molecules, intermixing of atomic orbitals only occurs when electronegativity value is similar to the two atoms. $CO$ molecule is composed of oxygen and carbon.
Oxygen is an electronegative element due to which it is stable and lower in energy. As the energy of oxygen is lower than that of carbon, the energy difference of $2s$ orbital of oxygen and carbon is very high. As in heteroatomic molecules electronegativity difference should be low, electronic configuration of $2s$ orbital will not be considered as their mixing will be low.
Electronic configuration of $CO$ molecules are similar to nitrogen (as the number of electrons is the same in both species).
Electronic configuration of $CO$ is found to be $1{\sigma ^2}2{\sigma ^2}1{\pi ^4}3{\sigma ^2}$ .

So, the correct answer is Option A.

Note: Molecules which have unpaired electrons have a net magnetic moment and are called paramagnetic. A molecule which doesn’t have unpaired electrons that molecule does not have a net magnetic moment and are called diamagnetic.