The bonding in diatomic molecules can be described by Molecular Orbital (MO) theory. Sigma ($\sigma$) bonds are formed by head-on overlap of atomic orbitals, while pi ($\pi$) bonds are formed by sideways overlap of p-orbitals. - For $ \text{C} _2 $, the molecular orbital configuration is $ (\sigma_{2s})^2 (\sigma^{}_{2s})^2 (\pi_{2p})^4 $. The bond order is 2, which arises solely from the filling of the $ \pi_{2p} $ bonding orbitals. Thus, $ \text{C}_2 $ has two $ \pi $ bonds. - For $ \text{O} _2 $, $ \text{N}_2 $, and $ \text{F}_2 $, the MO configurations involve filling of both $ \sigma $ and $ \pi $ bonding orbitals, indicating the presence of at least one $ \sigma $ bond along with $ \pi $ bonds.