Nitrous oxide. Molecular model of the gas nitrous oxide (N2.O), also known as laughing gas. This colourless non-flammable gas is used in surgery and dentistry for its anaesthetic and analgesic effects. It is one of the primary greenhouse gases in the Earth's atmosphere. Atoms are represented as spheres and are colour-coded: nitrogen (blue) and oxygen (red). The molecule's energy surface is also shown in partially sectioned view.