Which molecular shape is common for carbon atoms with all single bonds?

The shape of a molecule is heavily influenced by the arrangement of its bonding electrons and lone pairs around a central atom, which can be predicted using the valence shell electron pair repulsion (VSEPR) theory. For carbon atoms that form four single covalent bonds, which is typical in many organic compounds, we observe the formation of a tetrahedral shape.

In a tetrahedral structure, the carbon atom is at the center with four substituents (e.g., other carbon atoms or hydrogen atoms) positioned at the corners of a tetrahedron. This arrangement minimizes the repulsion between the bonding electron pairs, as they are spread out as far as possible, leading to an optimal geometry.

Each bond angle in a perfect tetrahedral arrangement is approximately 109.5 degrees, which is the result of this spatial arrangement. This geometry perfectly accommodates carbon's tetravalency, where it can form four single bonds with other atoms.

In contrast, other shapes like linear (180 degrees), trigonal planar (120 degrees), or trigonal pyramidal (approximately 107 degrees) would not accommodate the four single bonds around carbon effectively. Therefore, tetrahedral is the correct description for the molecular shape of carbon atoms bonded only by single bonds.