Question

Give the electron-domain and molecular geometries of a molecule that has the following electron domains on its central atom: (a) four bonding domains and no nonbonding domains, (b) three bonding domains and two nonbonding domains, (c) five bonding domains and one nonbonding domain, (e) four bonding domains and two nonbonding domains.

Short answer

(a) Electron-domain geometry: Tetrahedral, Molecular geometry: Tetrahedral. (b) Electron-domain geometry: Trigonal Bipyramidal, Molecular geometry: T-shaped. (c) Electron-domain geometry: Octahedral, Molecular geometry: Square Pyramidal. (e) Electron-domain geometry: Octahedral, Molecular geometry: Square Planar.

Step-by-step solution

(a) Four bonding domains and no nonbonding domains

In this case, the central atom has four bonding domains and no nonbonding domains. According to the VSEPR theory, the electrons will arrange themselves in a tetrahedral arrangement to minimize repulsion. Electron-domain geometry: Tetrahedral Molecular geometry: Tetrahedral

(b) Three bonding domains and two nonbonding domains

Here, the central atom has three bonding domains and two nonbonding domains. In this situation, the electron pairs will arrange themselves in a trigonal bipyramidal arrangement. The nonbonding domains will occupy the two equatorial positions since they experience less repulsion here as compared to the axial positions. Electron-domain geometry: Trigonal Bipyramidal Molecular geometry: T-shaped

(c) Five bonding domains and one nonbonding domain

In this scenario, the central atom has five bonding domains and one nonbonding domain. The electron pairs will adopt an octahedral arrangement to minimize repulsion. The nonbonding domain will take up one of the equatorial positions. Electron-domain geometry: Octahedral Molecular geometry: Square Pyramidal

(e) Four bonding domains and two nonbonding domains

In this case, the central atom has four bonding domains and two nonbonding domains. The electron pairs will arrange themselves in an octahedral arrangement to minimize repulsion. The two nonbonding domains will occupy the opposite equatorial positions. Electron-domain geometry: Octahedral Molecular geometry: Square Planar