Total number of species from the following with central atom utilising $2p^2$ hybrid orbitals for bonding is _______.
$\text{NH}_3, \, \text{SO}_2, \, \text{SiO}_2, \, \text{BeCl}_2, \, \text{C}_2\text{H}_2, \, \text{C}_2\text{H}_4, \, \text{BCl}_3, \, \text{HCHO}, \, \text{C}_6\text{H}_6, \, \text{BF}_3, \, \text{C}_2\text{H}_4\text{Cl}_2$