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Why can carbon form four covalent bonds in a tetrahedral arrangement?

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Diagram showing the formation of a polar covalent bond in a water molecule, with two hydrogen atoms bonding to one oxygen atom to form H2O, illustrating shared electrons and chemical reaction. — covalent bond In polar covalent bonds, such as that between hydrogen and oxygen atoms, the electrons are not transferred from one atom to the other as they are in an ionic bond. Instead, some outer electrons merely spend more time in the vicinity of the other atom. The effect of this orbital distortion is to induce regional net charges that hold the atoms together, such as in water molecules.

Carbon atoms can form four covalent bonds in a tetrahedral arrangement due to a process called hybridization.

While a carbon atom in its ground state has a valence-shell electron configuration of $2 s^{2} 2 p_{x}^{1} 2 p_{y}^{1}$ , which would suggest it could only form two bonds, it can undergo a process of promotion where an electron is elevated to a higher orbital, resulting in a $2 s^{1} 2 p_{x}^{1} 2 p_{y}^{1} 2 p_{z}^{1}$ configuration.1

To resolve the discrepancy between its atomic orbitals and the experimentally observed equivalence of its four bonds in molecules like methane, carbon undergoes hybridization—the mixing of its one $2 s$ and three $2 p$ orbitals. This creates four equivalent $s p^{3}$ hybrid orbitals. These orbitals are lobelike and orient themselves toward the four corners of a regular tetrahedron, making angles of approximately 109.5° with each other. This geometry minimizes electron repulsion and provides the most stable arrangement for the four covalent bonds.234