(a) An AB2 molecule is linear. How many nonbonding electron pairs are around the A atom from this information?

Verified step by step guidance

1. Identify the molecular geometry of the AB2 molecule. Given that the molecule is linear, this implies that the arrangement of atoms and electron pairs around the central atom A is in a straight line.
2. Recall VSEPR theory, which states that the shape of a molecule is determined by the repulsions between all electron pairs surrounding the central atom, including bonding and nonbonding pairs.
3. Determine the hybridization of the central atom A. For a linear shape in an AB2 molecule, the central atom typically has sp hybridization.
4. Understand that in sp hybridization, the central atom A has one s orbital and one p orbital mixing to form two sp hybrid orbitals, which are used to form sigma bonds with the two B atoms.
5. Conclude that since all available orbitals in sp hybridization are used for bonding and the molecule is linear, there are no nonbonding electron pairs (lone pairs) on the central atom A.

Key Concepts

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory is used to predict the geometry of molecules based on the repulsion between electron pairs around a central atom. In the case of an AB2 molecule, the arrangement of bonding and nonbonding electron pairs determines the molecular shape, which in this instance is linear.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. For an AB2 molecule that is linear, the two B atoms are positioned 180 degrees apart, indicating that the central atom A has no lone pairs of electrons affecting the geometry, which is crucial for determining the number of nonbonding electron pairs.

Lone Pairs

Lone pairs are pairs of valence electrons that are not involved in bonding and are localized on a single atom. In a linear AB2 molecule, the absence of lone pairs on the central atom A allows for the linear shape, indicating that there are zero nonbonding electron pairs around A.