Question

predict the molecular geometry of this molecule:
step 1
select the electron - pair geometry for this molecule. check your answer.
step 2
place terminal atoms in the appropriate positions on the molecule. check your answer.
step 3
enter the molecular geometry for this molecule.
molecular geometry:

Explanation:

Step 1: Analyze the molecule (BF₃)

The molecule is \( \text{BF}_3 \) (boron trifluoride). Boron has 3 valence electrons, and each fluorine contributes 1 electron to the bond. So, the central boron atom is bonded to 3 fluorine atoms, and there are no lone pairs on the boron atom.

Step 2: Determine electron - pair geometry

For a central atom with 3 bonding pairs and 0 lone pairs, the electron - pair geometry (which in this case is the same as molecular geometry since there are no lone pairs) is trigonal planar. The formula for determining the geometry is based on the VSEPR (Valence Shell Electron Pair Repulsion) theory. The number of bonding pairs (\( BP \)) and lone pairs (\( LP \)) around the central atom determines the geometry. For \( \text{BF}_3 \), \( BP = 3 \), \( LP=0 \). The general formula for the geometry when \( BP + LP=3 \) and \( LP = 0 \) is trigonal planar.

Step 3: Confirm molecular geometry

Since there are no lone pairs of electrons on the central boron atom, the molecular geometry is the same as the electron - pair geometry. The repulsion between the three bonding pairs (B - F bonds) is minimized when they are arranged in a trigonal planar geometry, with bond angles of approximately \( 120^{\circ} \) between each B - F bond.

Answer:

trigonal planar