Answer:
The first and third digit of the VSEPR notation indicate the number of electron groups and lone pairs on the central atom, respectively. This information is used to determine the molecular geometry of a molecule. For example, in the notation AX3E2, the first digit "3" represents three electron groups around the central atom, while the third digit "2" represents two lone pairs on the central atom, leading to a trigonal bipyramidal molecular geometry.
Step-by-step explanation:
The VSEPR (Valence Shell Electron Pair Repulsion) number is a shorthand notation used to describe the molecular geometry of a molecule based on the number of electron groups (bonding and non-bonding) around the central atom.
The first digit of the VSEPR number indicates the number of electron groups around the central atom, while the third digit indicates the number of lone pairs on the central atom.
For example, in the VSEPR notation AX3E2, the first digit "3" indicates that there are three electron groups around the central atom, and the third digit "2" indicates that there are two lone pairs on the central atom. This notation corresponds to a trigonal bipyramidal molecular geometry, where three bonding pairs and two lone pairs are arranged symmetrically around the central atom.