Question: why bcl3 is trigonal planar?
Answer: BCl3 has 3 B-Cl single bonds and no lone pair around B, hence 6 valence electrons around B. As per VSEPR notation, this molecule takes AX3 notation. The geometry of BCl3 is trigonal planar. ... AlCl3 has 3 Al-Cl single bonds and no lone pair around Al, hence 6 valence electrons around Al.