2s and 2p atomic orbitals combine, forming σ (sigma) and π (pi) molecular orbitals. σ orbitals result from head-on overlap, while π orbitals arise from sideways overlap. This molecular orbital theory explains the bonding in molecules

$\mathrm{}$ $2\mathrm{s}$ orbital will form, two molecular orbitals $\mathrm{\sigma }2 \mathrm{s}$ and $\mathrm{\sigma }*2 \mathrm{s}$.
$2\mathrm{p}$ orbital will form six molecular orbitals $\mathrm{\sigma }2{\mathrm{p}}_{\mathrm{z}}$ and $\mathrm{\sigma }*2{\mathrm{p}}_{\mathrm{z}}$. $\mathrm{\pi }2{\mathrm{p}}_{\mathrm{x}},\mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}$ and $\mathrm{\pi }*2{\mathrm{p}}_{\mathrm{x}},\mathrm{\pi }*2{\mathrm{p}}_{\mathrm{y}}$

Hence the total number of molecular orbitals formed from $2\mathrm{s}$ and $2\mathrm{p}$ atomic orbitals of a diatomic molecule formed is $8$.