Is \[{C_2}\] paramagnetic or diamagnetic?

Hint: To find out whether a molecule is paramagnetic or diamagnetic one must know the molecular electronic configuration of the molecule. When the molecule has unpaired electrons then the molecule is paramagnetic in nature, while having paired electrons it is diamagnetic in nature.

Complete answer:
Before answering the question let us understand what magnetic moments are and their classification.
As we have learned in the atomic theory, electrons present in the atom move around the nucleus in the circular orbits. This motion gives rise to the orbital magnetic moment. This magnetic moment is the result of the vector sum of the orbital and spin magnetic moment. Based on their magnetic properties they are classified as ferromagnetic, paramagnetic and diamagnetic.
Diamagnetic substance- They have weak, negative susceptibility to magnetic fields. In the diamagnetic materials all the electrons are paired so there is no permanent net magnetic moment per atom. As soon as the external field is removed they do not retain their magnetic properties.
Paramagnetic substance- They have a small, positive, susceptibility to magnetic fields. They do not retain their magnetic properties when the external field is removed. Paramagnetic property is due to the presence of some unpaired electrons and the realignment of electrons caused by external magnetic fields.
Now that we know these terms let us start by checking the electronic configuration of \[carbon\] atoms which is- \[1{s^2}2{s^2}2{p^2}\]
Molecular electronic configuration is \[\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}{(\pi 2{p_y})^2}{ = ^2}{(\pi 2{p_z})^2}\]
It is clear from the above molecular configuration that \[{C_2}\] has paired electrons and is therefore diamagnetic in nature.

Note:
Ferromagnetic substances have large, positive susceptibility to magnetic fields. They have unpaired electrons and therefore have net magnetic moment as well as retain their magnetic properties after the removal of external fields.