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Why does methane have a tetrahedral arrangement of hydrogen atoms around carbon?

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Diagram showing four types of crystal bonding: ionic bonding with sodium and chlorine ions, covalent bonding with carbon atoms sharing electrons, metallic bonding with iron ions surrounded by free electrons, and molecular bonding with hydrogen molecules held by weak electrical attraction. — chemical bonding Different types of bonding in crystals.

The tetrahedral arrangement of hydrogen atoms around the central carbon in methane (CH₄) is explained by two primary chemical theories:

Valence Bond Theory and Hybridization

From the perspective of valence bond theory, the carbon atom undergoes a process called hybridization. By mixing its 2s and three 2p orbitals, the carbon atom creates four equivalent sp³ hybrid orbitals. These orbitals are oriented toward the four corners of a regular tetrahedron, allowing each to form an identical σ bond with a hydrogen 1s electron.1

VSEPR Theory

VSEPR theory (Valence Shell Electron Pair Repulsion theory) explains the shape based on electron repulsion. The carbon atom in methane is surrounded by four bonding electron pairs. To minimize mutual repulsion, these pairs adopt a tetrahedral disposition, maximizing their separation at an angle of 109.5°. Because each pair is attached to a hydrogen atom, the resulting molecular geometry is tetrahedral.23