All practice pages/Interatomic theory/Elements
Element 10, a noble gas
The gas that glows red-orange in a sign tube, and one of the least reactive substances there is.
Period 2, group 18. The other noble gases are tinted, and every cell opens its own article.
Neon has 10 electrons, one for every proton, so the atom carries no charge. Below are the same 10 electrons written two ways.
1s² 2s² 2p⁶
Short form: [He] 2s² 2p⁶, where [He] stands for the 2 electrons helium already has.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 2 here is 2s² 2p⁶, and 2 + 6 is 8.
Neon sits in period 2 and has 2 shells. The period number counts the shells.
The outer shell holds 8 electrons. Those are the ones neon can lose, gain or share, so they are the ones that decide what it bonds with. For a main-group element the group number gives that count: group 18 means 8.
A full valence shell, so it has almost no tendency to gain, lose or share electrons, and it exists as single atoms.
About 18 parts per million of air. It is the fifth most abundant element in the universe but rare on Earth, because as a light, unreactive gas it escaped into space while the planet formed. All of it is collected as a byproduct of separating liquid air into oxygen and nitrogen.
William Ramsay and Morris Travers found it in 1898 by slowly boiling liquid air and examining each fraction; it glowed crimson in their spectrum tube. Ramsay's 13-year-old son suggested the Latin novum, new, and they chose the Greek neos instead.
Neon signs, though only the red-orange ones are pure neon; other colors come from argon, mercury vapor and colored glass or coatings. Neon also goes into the lasers that print patterns on computer chips, helium-neon lasers, high-voltage indicators and, as a liquid, cryogenic cooling.