Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Neon, symbol Ne, colorless, odorless, nonreactive gaseous element that makes up a tiny fraction of Earth's atmosphere. A member of group 18 (or VIIIa) of the periodic table, neon is one of the noble gases. The atomic number of neon—that is, the number of protons in the nucleus of a neon atom—is 10.

British chemists Sir William Ramsay and Morris Travers first separated neon from other noble gases in 1898. Neon and the other noble gases do not normally form compounds with other elements. During the past few decades chemists have managed to induce several of the noble gases to form compounds with other extremely reactive elements, such as fluorine, but neon and helium have so far resisted these efforts. Neon melts at -248.59°C (-415.46°F), boils at -246.08°C (-410.94°F), and has a specific gravity of 0.8999 at 0°C (32°F). The atomic weight of neon is 20.18.

Stars much more massive than the Sun produce neon during the later stages of nuclear fusion. The abundance of neon on Earth is lower than in the universe generally. Neon constitutes just 15 parts per million in the atmosphere.

Neon is obtained for commercial purposes from air by the process of fractional distillation. In this process, air is cooled until it liquefies, and then it is gradually allowed to warm. The tiny fraction of the air that boils off at -246.08°C is neon, which is then collected. Some minerals also contain tiny amounts of trapped neon gas.

Neon occurs naturally as three stable isotopes. These isotopes are neon-20, which is the most abundant isotope; neon-22; and neon-21. All isotopes of an element have the same number of protons in their nuclei but have differing numbers of neutrons. The first demonstration of the existence of multiple stable isotopes of a single element was performed with neon in 1912.


Neon gas produces a distinctive reddish-orange glow when an electric current is forced through a tube containing the gas at a low pressure. These vacuum electric-discharge tubes are used extensively in the familiar neon light of advertising displays. The term neon light is often incorrectly applied to discharge tubes filled with gases other than neon that produce a colored glow (see Neon Lamp). Other uses of neon include in television tubes, gas lasers, and high-voltage indicators. Liquid neon is used as a cryogenic refrigerant. It has over 40 times more refrigerating capacity per unit volume than liquid helium.