Sigma electrons are a type of electron that participate in the formation of sigma bonds, which are the strongest type of covalent bonds. These electrons are found in the overlapping regions of atomic orbitals, where they create a bond between two atoms. Sigma bonds can occur between different types of atoms, such as in molecules like H2O or CH4. In a sigma bond, the electron density is concentrated along the axis connecting the two nuclei, allowing for free rotation around the bond. This characteristic is essential in determining the shape and reactivity of molecules, influencing their properties and interactions in chemical reactions.