Final answer:
Boron trichloride (BCl3) has three single bonds between the central boron atom and each of the three chlorine atoms, resulting in a trigonal planar molecular geometry.
Step-by-step explanation:
The molecule boron trichloride (BCl3) possesses three single bonds. In the Lewis structure for BCl3, the central boron atom contributes three valence electrons, and each chlorine atom contributes seven valence electrons. Thus, each chlorine atom forms a single covalent bond with the boron atom. There are no lone pairs of electrons on the central boron atom, resulting in a trigonal planar electron-pair geometry. The arrangement of three regions of high electron density around the central boron atom confirms that BCl3 has three bonding pairs, giving it a trigonal planar molecular geometry with 120° angles between the B-Cl bonds. Additionally, boron tends to form compounds with an incomplete octet, as it only has six valence electrons when three chlorine atoms are bonded to it.