Neon (Ne)
Neon (Ne) is a noble gas with atomic number 10 and a standard atomic weight of 20.180. At room temperature it is a gas that melts at -249 °C and boils at -246 °C.
Neon key facts
Neon at a glance
Identity
| Symbol | Ne |
|---|---|
| Atomic number (Z) | 10 |
| Atomic weight | 20.180 ± 0.001 (CIAAW 2024) |
| Category | Noble gas |
| Group | 18 — noble gases |
| Period | 2 |
| Block | p-block |
| CAS number | 7440-01-9 |
Atomic properties
| Electron configuration | [He] 2s2 2p6 Full: 1s2 2s2 2p6 |
|---|---|
| Electrons per shell | 2, 8 |
| First ionisation energy | 21.564 eV (2,080.7 kJ/mol) 2nd: 40.963 eV · 3rd: 63.423 eV |
| Atomic radius (empirical) | 160 pm |
| Covalent radius | 67 pm |
| Van der Waals radius | 154 pm |
Physical properties
| State at 25 °C | Gas |
|---|---|
| Melting point | -248.6 °C · -415.5 °F · 24.56 K |
| Boiling point | -246 °C · -410.9 °F · 27.1 K |
| Density | 0.9002 g/L (gas at 0 °C, 1 atm) |
| Specific heat capacity | 1.03 J/(g·K) |
| Crystal structure | Face-centred cubic |
Isotopes & abundance
| Natural occurrence | Primordial |
|---|---|
| Radioactive | No |
| Natural isotopes (abundance) | 20Ne 90.48%, 22Ne 9.25%, 21Ne 0.27% |
| Stable isotopes | 4 |
| Known isotopes | 20 |
| Abundance in Earth's crust | 0.005 mg/kg |
| Abundance in seawater | 0.00012 mg/L |
Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.
Neon electron configuration
Neon has 10 electrons. Written in short form, its ground-state configuration is [He] 2s2 2p6 — the electrons of the noble gas helium, plus 2s2 2p6.Written out in full: 1s2 2s2 2p6.
As a member of group 18 it has 8 valence electrons in its outer shell (shell 2), which largely decide its chemistry — a full outer shell, which is why it is so unreactive.
Discovery and name
1898 — William Ramsay and Morris Travers · England.
Greek neos, new.
Known for
An inert noble gas that glows red-orange in discharge tubes — the original 'neon sign'. Also used in helium–neon lasers and as a cryogenic refrigerant.
Isotopes of neon
Naturally occurring neon is a mix of 3 isotopes. Each has 10 protons; they differ in the number of neutrons:
| Isotope | Protons | Neutrons | Natural abundance | Stability |
|---|---|---|---|---|
| 20Ne | 10 | 10 | 90.48% | stable |
| 22Ne | 10 | 12 | 9.25% | stable |
| 21Ne | 10 | 11 | 0.27% | stable |
20 isotopes of neon are known in our data set (half-lives as published in nuclear data tables).
Neon compared with group 18
The other elements in group 18 (noble gases), from top to bottom of the table:
| Element | Z | Atomic weight | Melting point | Boiling point | Density | Electronegativity |
|---|---|---|---|---|---|---|
| Helium | 2 | 4.0026 | — | -269 °C | 0.1786 g/L | — |
| Neon | 10 | 20.180 | -249 °C | -246 °C | 0.9002 g/L | — |
| Argon | 18 | 39.95 | -189 °C | -186 °C | 1.784 g/L | — |
| Krypton | 36 | 83.798 | -157 °C | -153 °C | 3.749 g/L | 3 |
| Xenon | 54 | 131.29 | -112 °C | -108 °C | 5.894 g/L | 2.6 |
| Radon | 86 | [222] | -71 °C | -62 °C | 9.73 g/L | 2.2 |
| Oganesson | 118 | [294] | — | — | 7 g/cm³ (pred.) | — |