Discuss the structures of alkanes.

Alkanes contain only carbon-carbon and carbon - hydrogen single bonds. For example methane.

Therefore, carbon in alkanes is sp³ - hybridised. Since sp³ hybridised carbon has four half filled sp³ - orbitals, therefore, it forms four σ-bonds. These four bonds are directed towards the corners of a regular tetrahedron. In other words, the angle between any two adjacent bonds is 109° - 28' (tetrahedral angle).
In methane molecule, carbon lies at the centre of the tetrahedron while the four hydrogens are present at the corners of vertices of the regular tetrahedron. This implies that; each face of the tetrahedron is an equilateral triangle and has three bonds.