Advanced Placement (AP) Chemistry Practice Exam

What is the bond angle in a tetrahedral geometry?

1. 120 degrees

2. 90 degrees

3. 109.5 degrees

4. 180 degrees

The correct answer is: 109.5 degrees

In a tetrahedral geometry, the bond angles are approximately 109.5 degrees. This geometry arises when a central atom is bonded to four other atoms with no lone pairs, resulting in a three-dimensional arrangement where the bonded atoms are spread out as far apart as possible to minimize electron pair repulsions. The tetrahedral shape is characterized by the four atoms positioned at the corners of a tetrahedron, which is a polyhedron with four triangular faces. The ideal bond angle of 109.5 degrees reflects the balance between the repulsive forces of the electron pairs surrounding the central atom, optimizing spatial distribution in three dimensions. Understanding tetrahedral geometry is critical in predicting molecular shapes and understanding molecular interactions, as it directly influences properties such as polarity and reactivity.