Total number of species from the following with central atom utilising \( \text{sp}^2 \) hybrid orbitals for bonding is __________
\( \mathrm{NH_3}, \ \mathrm{SO_2}, \ \mathrm{SiO_2}, \ \mathrm{BeCl_2}, \ \mathrm{C_2H_2}, \ \mathrm{C_2H_4}, \ \mathrm{BCl_3}, \ \mathrm{HCHO}, \ \mathrm{C_6H_6}, \ \mathrm{BF_3}, \ \mathrm{C_2H_4Cl_2} \)