Question

Why is the basic shape of alkanes tetrahedral?

Answer 1

Because the carbon is sp³ hybrid.

Explanation:

The carbon is member from the 14th family in the periodic table. It also has 6 electrons (atomic number = 6). When we distribute those electrons, we create `1s^2 2s^2 2p^2`, but the carbon has to lower the `2p` orbitals and raise the `2s` orbitals in energy, making its `2s` and `2p` orbitals degenerate, as four `sp^3` hybridized orbitals, with one electron in each, before bonding.

Carbon needs 4 more electrons to become stable, and it gets those electrons by 4 covalent bonds.

The tetrahedral geometry is created because every single `sp^3` electron from the carbon repels the other with an equal coulombic force (wouldn't be equal if the carbon wasn't hybridized) in the s¹p³ (sp³) orbital. This creates an equal distribution to the atoms and gives it a tetrahedral geometry.