Question

According to M.O. theory for the atomic species "${{C}_{2}}$ " which is not correct? (This question has multiple correct options)
a.) Bond order is zero and it is paramagnetic.
b.) Bond order is zero and it is diamagnetic.
c.) Bond order is two and it is paramagnetic
d.) Bond order is two and it is diamagnetic

Answer 1

Before solving this question, we should have prior knowledge about Paramagnetism. Paramagnetic substances are those which have unpaired electrons. The paramagnetic substances induced a magnetic field in the direction of the external magnetic field.

Complete step by step answer:
- Bond order is calculated by dividing the number of bonds with the total number of bonding pairs. The bond length is inversely proportional to the bond length. This means that more will be the bond order less will be the bond length. The bond order of triple bond is highest and similarly the bond length of triple bond is lowest.
- The formula to calculate bond order is:
$bond\text{ order=}\frac{1}{2}(\text{bonding electrons- nonbonding electrons)}$
Bonding electrons in ${{C}_{2}}$=8
Number of nonbonding electrons in ${{C}_{2}}$=4
Bond order of ${{C}_{2}}$= $\dfrac{1}{2}(8-4)=2$
And there are no unpaired electrons, hence, ${{C}_{2}}$ is diamagnetic.
The correct option is option “D” .

Additional Information . Paramagnetism is the form of magnetism which is exhibited by some substances and the compounds by which they are weakly or partially attracted by the magnetic field. The paramagnetic substances induced a magnetic field in the direction of the external magnetic field. The substances are paramagnetic when they have unpaired electrons.

Note: The paramagnetic theory is explained by the molecular orbital theory. For example, oxygen molecules are paramagnetic although there are a total of 16 electrons present in oxygen. This property of oxygen is explained by the MOT.