Which are the type of molecular orbitals ? Give information in short.

Molecular orbitals of diatomic molecules are designated or $\sigma$ (sigma), $\pi$ (Pi), $\delta$ (Delta) etc. $\sigma$ (sigma) molecular orbitals : The sigma $(\sigma)$ molecular orbitals are symmetrical around the bond axis.

e.g. $\sigma_{1 s}$ and $\sigma_{1 s}^{*}$ : The linear combination of $1 s$ orbitals centered on two nuclei produces two molecular orbitals which are symmetrical around the bond-axis. Such molecular orbitals are of the $\sigma$ type and are designed as $\sigma 1 s$ and $\sigma^{*} 1 s \mathrm{eg} . \sigma 2 p_{z}$ and $\sigma \mathbb{R} p_{z}:$ If internuclear axis is taken to be in the Z-direction, it can be seen that a linear combination of $2 p_{z}$ orbitals of two atoms also produces two sigma molecular orbitals designated or $\sigma\left(2 p_{z}\right), \sigma^{*}\left(2 p_{z}\right)$.

$\sigma(1 s), \sigma^{*}(1 s), \sigma(2 s), \sigma^{*}(2 s), \sigma\left(2 p_{z}\right), \sigma^{*}\left(2 p_{z}\right)$ are $\sigma$ types and symmetrical around the bond axis.

$\pi$ and $\pi^{*}$ types molecular orbitals : The $\pi$ molecular orbitals are not symmetrical around the bond axis because in these above and below the bond axes $(+)$ and $(-)$ symbol are not symmetrical.

Molecular orbitals obtained form $2 p_{x}$ and $2 p_{y}$ orbitals are not symmetrical around the bond axis because of the presence of positive lobes above and negative lobes below the molecular plan. Such molecular orbitals are labelled as $\pi$ and $\pi^{*}$.

A $\pi$ bonding $MO$ has larger electron density above and below the inter nuclear axis.

The $\pi^{*}$ antibonding $MO$ has a node between the nuclei.