Helium vs Neon
Both are noble gass, so they share the same broad chemistry.
The differences in plain English
- They sit in the same column, group 18, so they have the same number of outer electrons and react in similar ways; the heavier one, Neon, is usually the more reactive of the two if they are metals, and the less reactive if they are non-metals.
- Both are gass at room temperature.
- Neon is denser, about 5.0 times more than Helium (0.9002 against 0.1786 g/L).
- Neon melts at -249 °C, Helium at -272 °C.
- An atom of Neon is about 5.0 times heavier than an atom of Helium (20.18 u against 4.00 u).
Side by side
| Helium | Neon | |
|---|---|---|
| Atomic number | 2 | 10 |
| Symbol | He | Ne |
| Family | Noble gas | Noble gas |
| Group / period | 18 / 1 | 18 / 2 |
| State at room temperature | Gas | Gas |
| Atomic mass | 4.003 u | 20.180 u |
| Density | 0.1786 g/L | 0.9002 g/L |
| Melting point | -272 °C | -249 °C |
| Boiling point | -269 °C | -246 °C |
| First ionisation energy | 2372.3 kJ/mol | 2080.7 kJ/mol |
| Electron configuration | 1s2 | [He] 2s2 2p6 |
| Discovered by | Pierre Janssen | Morris Travers |
Helium
Helium is the second lightest element and the least reactive of them all. It is a colourless gas with no smell or taste, and it refuses to form stable compounds with anything under normal conditions. Every helium atom has two protons and two electrons, and those two electrons completely fill its only shell. That full shell is the reason helium is so aloof.
- Helium was identified in sunlight in 1868, decades before it was found on Earth.
- Liquid helium cooled below about minus 271 degrees Celsius becomes a superfluid with zero viscosity that can climb the walls of an open container.
Neon
Neon is a noble gas so unreactive that in more than a century nobody has made a stable compound of it. It is colourless, odourless and invisible, until you pass an electric current through it. Then it shines with a red-orange light that is unmistakable and has been drawing eyes to shop windows since 1910.
- Neon is the fifth most abundant element in the universe, but only about 18 parts per million of Earth's air.
- Only the red-orange colour in a neon sign actually comes from neon. Other colours use different gases or coated glass.
Colour the bubbles by density or melting point and the difference jumps out.
More comparisons
Data from Periodic-Table-JSON (CC BY-SA); temperatures rounded to the nearest degree. Written by Anthony.