What is the molecular geometry of PCl3

a. trigonal pyramidal
b. see-saw
c. tetrahedral
d. T-shape

http://www.tutor-pages.com/Chemistry/Molecular_Geometry/050_Phosphorus_Trichloride_PCl3.html

Trigonal pyramid

The molecular geometry of PCl3 is (a) trigonal pyramidal.

To determine the molecular geometry of PCl3, we need to follow a few steps:

Step 1: Determine the Lewis structure of PCl3.
First, we need to determine the central atom, which is Phosphorus (P). Next, we need to determine the number of valence electrons for each atom. Phosphorus is in Group 5A, so it has 5 valence electrons, and each Chlorine (Cl) atom has 7 valence electrons. To calculate the total number of valence electrons, we add these numbers together: 5 + (3 Ă— 7) = 26 valence electrons.
Using the octet rule, we distribute the electrons around the central atom, ensuring that each atom is surrounded by eight electrons (except hydrogen, which has two electrons) and that all electrons are accounted for. In this case, we place three lone pairs of electrons around each chlorine atom and one lone pair of electrons around the phosphorus atom.

Step 2: Determine the electron pair geometry.
The electron pair geometry describes the arrangement of all electron pairs surrounding the central atom. In this case, PCl3 has one central atom and three bonded atoms, with no lone pairs on the central atom. Therefore, the electron pair geometry is trigonal planar.

Step 3: Determine the molecular geometry.
The molecular geometry describes the arrangement of the bonded atoms around the central atom, excluding the lone pairs. In the case of PCl3, there are three bonded atoms (Cl atoms) and no lone pairs on the central atom (P). Since there are no lone pairs on the central atom, the molecular geometry is the same as the electron pair geometry—trigonal planar.

Therefore, the molecular geometry of PCl3 is:
c. trigonal planar