For a molecule with a tetrahedral geometry, what is the expected bond angle?

In a molecule with tetrahedral geometry, the expected bond angle is approximately 109.5 degrees. This geometry occurs when a central atom is bonded to four other atoms, creating a three-dimensional shape where the bonded atoms are arranged to minimize repulsion according to VSEPR (Valence Shell Electron Pair Repulsion) theory.

The tetrahedral arrangement allows the four electron pairs (one for each bond) to be spread as far apart as possible, leading to the characteristic bond angles. In a perfect tetrahedron, the angles between any two bonds are 109.5 degrees. This geometrical arrangement is observed in common molecules such as methane (CH₄).

The other angles mentioned do not reflect the tetrahedral geometry: 90 degrees corresponds to the geometry found in octahedral arrangements, 120 degrees is typical of trigonal planar structures, and 180 degrees refers to linear geometries.