A molecule with the formula AB₃ has a trigonal planar geometry. How many electron groups are on the central atom?

Verified step by step guidance

1. Identify the molecular geometry given in the problem, which is trigonal planar.
2. Recall that a trigonal planar geometry is associated with a central atom surrounded by three atoms in a plane, forming 120-degree bond angles.
3. Understand that the geometry is determined by the number of electron groups around the central atom, which include both bonding pairs and lone pairs of electrons.
4. Recognize that in a trigonal planar geometry, there are no lone pairs on the central atom, only bonding pairs.
5. Conclude that the number of electron groups on the central atom is equal to the number of atoms bonded to it, which is 3 in this case.

Key Concepts

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. In the case of AB3, where A is the central atom and B represents the surrounding atoms, the trigonal planar geometry indicates that the three B atoms are arranged around A in a flat, triangular shape, with bond angles of approximately 120 degrees.

Electron Groups

Electron groups include all regions of electron density around a central atom, which can be lone pairs, single bonds, double bonds, or triple bonds. In the context of the AB3 molecule, the central atom A has three bonding pairs of electrons associated with the three B atoms, leading to a total of three electron groups.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of molecules based on the repulsion between electron pairs. According to VSEPR, electron groups will arrange themselves to minimize repulsion, which helps determine the molecular shape, such as the trigonal planar configuration observed in AB3.