Neon (Ne). Diagram showing the nuclear composition and electron configuration of an atom of neon-20 (atomic number: 10), the most common isotope of the element neon. The nucleus consists of 10 protons (red) and 10 neutrons (yellow). Ten electrons (white) bind to the nucleus in shells (rings), filling the outer (second) electron shell in what is a very stable configuration. The stability of an element's outer electrons determines its chemical and physical properties. Neon is a noble gas in group 18, period 2, and the p-block of the periodic table. An inert gas found in trace amounts in the atmosphere, it is used in neon lamps and discharge tubes.