A sigma (σ) bond is a type of covalent bond that is formed when two atomic orbitals overlap directly between the two bonding atoms, allowing electrons to be shared between them.

A single bond consists of a σ-bond.

A pi (π) bond is a bond formed by the sideways overlap of two p-orbitals, with the electron density above and below the plane of the bonding atoms.

In sp, sp², and sp³ hybridisation, carbon atoms combine their atomic orbitals to form hybrid orbitals. This allows carbon to form stronger and more directional covalent bonds with other atoms.

Molecules containing sp³ hybridised atoms have a tetrahedral shape, with bond angles of 109.5°. This shape results from the arrangement of four σ-bonds around the central atom.

Molecules containing sp² hybridised atoms have a trigonal planar shape, with bond angles of 120°. This shape results from the arrangement of three σ-bonds around the central atom.

Molecules containing sp hybridised atoms have a linear shape, with a bond angle of 180°. This shape results from the arrangement of two σ bonds around the central atom.

A planar molecule is one in which all the atoms lie in the same plane.

Molecules containing sp² hybridised atoms, like ethene, are examples of planar molecules.

Sigma (σ) bonds result from head-on overlap of atomic orbitals, while pi (π) bonds result from side-to-side overlap of p-orbitals.

In a double bond, there is one sigma (σ) bond and one pi (π) bond.

In a triple bond, there is one sigma (σ) bond and two pi (π) bonds.