What is the bond angle Cl-B-Cl and molecular geometry of BCl_3...

The central atom in $\text{BCl}_3$ is Boron (B).

The number of valence electrons in Boron is $3$. It forms $3$ single bonds with $3$ Chlorine atoms.

Number of bond pairs = $3$
Number of lone pairs = $0$

Steric number = Bond pairs + Lone pairs = $3 + 0 = 3$

A steric number of $3$ corresponds to $sp^2$ hybridization.

Since there are no lone pairs on the central atom, the molecular geometry is trigonal planar.

The bond angle for a regular trigonal planar geometry is 120^{}^{\circ}.

Answer: 120^{}^{\circ} and trigonal planar