ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

In a tetrahedral geometry, the bond angle between the atoms is approximately 109.5 degrees. This arrangement occurs when a central atom is bonded to four other atoms, with the bonds distributed uniformly in three-dimensional space. The geometry seeks to minimize the repulsion between the electron pairs surrounding the central atom, as described by VSEPR (Valence Shell Electron Pair Repulsion) theory.

The tetrahedral shape allows for each bond angle to be as far apart as possible, resulting in the specific angle of 109.5 degrees. This angle is a consequence of the spatial orientation of the four groups around the central atom, leading to the characteristic three-dimensional structure seen in molecules like methane (CH₄) or ammonium (NH₄⁺). This angle is distinct from other geometries: for example, the 120-degree angle is characteristic of trigonal planar geometry, while 90 degrees is seen in octahedral arrangements, and 180 degrees corresponds to linear geometries. Thus, the tetrahedral bond angle is uniquely defined as approximately 109.5 degrees.