An AB2 molecule is described as having a tetrahedral geometry. (b) Based on the information given, which of the following is the molecular geometry of the molecule: (i) linear, (ii) bent, (iii) trigonal planar, or (iv) tetrahedral?

Verified step by step guidance

1. Step 1: Understand the molecular geometry. The molecular geometry of a molecule describes the three-dimensional shape of the atoms that make up a molecule. It is determined by the number of bonding pairs and lone pairs around the central atom.
2. Step 2: Identify the central atom. In an AB2 molecule, the central atom is 'A', and it is bonded to two 'B' atoms.
3. Step 3: Understand the tetrahedral geometry. A tetrahedral geometry means that the molecule is shaped like a tetrahedron, with the central atom at the center and the other atoms at the corners. In a tetrahedral molecule, there are four electron pairs around the central atom, which are arranged in such a way to minimize repulsion.
4. Step 4: Apply the information to the given molecule. The AB2 molecule is described as having a tetrahedral geometry. This means that in addition to the two 'B' atoms, there must be two lone pairs of electrons on the 'A' atom to make up the four electron pairs required for a tetrahedral geometry.
5. Step 5: Determine the molecular geometry. The molecular geometry is determined by the positions of the atoms, not the electron pairs. Therefore, the molecular geometry of the AB2 molecule is 'bent' or 'V-shaped', because the two 'B' atoms and the 'A' atom form a bent shape, while the two lone pairs of electrons on the 'A' atom do not contribute to the shape of the molecule.

Key Concepts

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is determined by the number of bonding pairs and lone pairs of electrons around the central atom, which influences the shape of the molecule. Understanding molecular geometry is crucial for predicting the physical and chemical properties of substances.

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 pairs will arrange themselves to minimize repulsion, leading to specific molecular shapes. This theory helps explain why certain molecules adopt geometries like tetrahedral or bent.

Tetrahedral Geometry

Tetrahedral geometry occurs when a central atom is bonded to four other atoms, with bond angles of approximately 109.5 degrees. This arrangement is typical for molecules with four bonding pairs and no lone pairs, such as methane (CH4). In the context of the question, recognizing that an AB2 molecule with tetrahedral geometry implies a specific arrangement is key to determining its molecular geometry.