$\mathrm{C}_{2}(\mathrm{Z}=6) 1 s^{2} 2 s^{2} 2 p^{2}$, So total electron in $\mathrm{C}_{2}=12$

Electron configuration in $\mathrm{MO}$ for $\mathrm{C}_{2}$ :

$(\sigma 1 s)^{2}\left(\sigma^{*} 1 s\right)^{2}(\sigma 2 s)^{2}\left(\sigma^{*} 2 s\right)^{2}\left(\pi 2 p_{x}\right)^{2}\left(\pi 2 p_{y}\right)^{2} \quad$ OR

$\mathrm{KK}(\sigma 2 s)^{2}\left(\sigma^{*} 2 s\right)^{2}\left(\pi 2 p_{x}\right)^{2}\left(\pi 2 p_{y}\right)^{2}$

Bond order $=\frac{1}{2}\left(\mathrm{~N}_{\mathrm{b}}-\mathrm{N}_{\mathrm{a}}\right)=\frac{1}{2}(8-4)=2$

Magnetic Property : All electrons are paired. So, diamagnetic.

Note: In $\mathrm{C}_{2}$ Molecule, the bond present in double bond are $\pi$-bond.

Energy diagram for $\mathrm{C}_{2}$ molecule :