We continue to review some of the most important materials in heat treatment and metallurgy.
Neon (chemical symbol: Ne)
Neon is a light, nontoxic, truly inert gas that is odorless, tasteless and colorless under normal conditions, but it glows with a reddish-orange color in a vacuum glow-discharge tube (Fig. 1). Being one of the periodic table’s noble gases, neon forms no known stable compounds.
At the atomic level, the outer shell of valence electrons are considered “full,” which is what gives noble gases a lesser tendency to chemically react with other elements. This natural inertness of noble gases makes them suitable for a number of applications. Neon is in a liquid state at 2.6ºC (36.7ºF) and has the narrowest liquid range of any element in the periodic table.
Neon was discovered in 1898 by William Ramsay and Morris Travers at University College London. Having previously known that one element can hide the presence of another, Ramsey and Travers used liquefied air to freeze a sample of argon. They then exposed the frozen argon to reduced pressure, in which they collected the first gas that was released.
When determining the spectrum of the new gas, the introduction of a high-voltage current to the neon in a vacuum tube yielded a bright crimson glow that had not been seen before. Ramsey and Travers were the first to experience what we now call a modern neon light. Ramsey named the new element neon after the Greek word, “neos,” which means “new.”
While neon is the fifth-most-abundant element in the universe, it only occupies about 0.0018% (18 ppm) of the earth’s atmosphere. Neon’s most common use is within vacuum tubes that make up neon signs, which were first developed and put to use over 100 years ago. It was quickly realized that heating and bending the glass vacuum tubes into letters made popular advertising signs, which are still prevalent today. When neon is liquefied, it is an important cryogenic refrigerant that has more than 40 times the cooling capacity per volume than liquid helium and three times more than liquid hydrogen.
Here are a few important facts about neon.[2,5]
- Atomic number: 10
- Atomic weight: 20.1797
- Melting point: 24.56 K (-248.59°C or -415.46°F)
- Boiling point: 27.07 K (-246.08°C or -410.94°F)
- Density: 0.0008999 grams per cubic centimeter
- Phase at room temperature: Gas
- Element classification: Nonmetal
- Period number: 2
- Group number: 18
- Group name: Noble gas
- Electron configuration: [He] 2s22p6