Image of a Methane molecule, CH4, an extremely strong greenhouse gas. Natural gas, as used is gas heating and electrical generation, is chiefly methane. Methane is released by biological processes. Methane is the first in a series of ALKANES, hydrocarbons that contain only single bonds (i.e. they are saturated hydrocarbons). Methane is a gas at normal temperatures. It is important as a greenhouse gas and as a fuel in natual gas. Methane consists of a central carbon atom covalently bonded to four hydrogen atoms. The bonds radiate out, as far away from each other as possible, towards the vertices of a regular tetrahedron. The carbon atom is shown as a black sphere at its covalent radius. The hydrogen atoms are shown as green spheres drawn at their covalent radii. The transparent bubble that surround the entire molecule represents the van der Waals surface of the molecule.