Describe the molecular geometry of:
(c) SiH₄

Verified step by step guidance

1. Step 1: Determine the central atom in the molecule. In SiH₄, silicon (Si) is the central atom because it is less electronegative than hydrogen (H) and can form more bonds.
2. Step 2: Count the total number of valence electrons. Silicon has 4 valence electrons, and each hydrogen has 1 valence electron. Therefore, the total number of valence electrons is 4 (from Si) + 4×1 (from H) = 8 valence electrons.
3. Step 3: Draw the Lewis structure. Place Si in the center and arrange the four hydrogen atoms around it, each forming a single bond with Si. This uses up all 8 valence electrons (4 bonds × 2 electrons per bond).
4. Step 4: Determine the electron pair geometry using VSEPR theory. SiH₄ has 4 bonding pairs and no lone pairs on the central atom. According to VSEPR theory, this arrangement corresponds to a tetrahedral electron pair geometry.
5. Step 5: Identify the molecular geometry. Since there are no lone pairs on the central atom, the molecular geometry is the same as the electron pair geometry, which is tetrahedral.

Key Concepts

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to VSEPR, electron pairs will arrange themselves as far apart as possible to minimize repulsion, leading to specific molecular shapes.

Tetrahedral Geometry

Tetrahedral geometry occurs when a central atom is bonded to four other atoms, with bond angles of approximately 109.5 degrees. In the case of SiH4, silicon is the central atom surrounded by four hydrogen atoms, resulting in a symmetrical tetrahedral shape that maximizes the distance between the bonding pairs of electrons.

Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate bonding. In SiH4, the silicon atom undergoes sp3 hybridization, where one s orbital and three p orbitals combine to create four equivalent sp3 hybrid orbitals, each forming a sigma bond with a hydrogen atom.