Helium
Definition and meaning of Helium in chemistry.
Helium is the second-lightest chemical element, a colorless, odorless, and chemically inert noble gas with atomic number 2 and symbol He.
In more detail
Its filled 1s² electron shell gives helium an extremely stable configuration and the highest first ionization energy of any element, so it forms essentially no stable chemical compounds under ordinary conditions. Helium has the lowest boiling point of any substance and cannot be frozen to a solid by cooling alone at normal pressure; it must also be compressed. Most terrestrial helium originates from alpha decay of heavy radioactive elements like uranium and thorium deep in Earth's crust, where it accumulates and is extracted from certain natural gas deposits.
Key facts
| Symbol | He |
|---|---|
| Atomic number | 2 |
| Boiling point | 4.22 K (-268.93°C) |
| Field | General Chemistry |
Liquid helium, which boils at 4.22 K (-268.93°C), is used to cool the superconducting magnets inside MRI scanners to their required operating temperature.
Frequently asked questions
Why doesn't helium form chemical compounds?
Its 1s² electron configuration is a complete, stable shell with no room for bonding electrons, and its very high ionization energy makes it extremely resistant to losing or sharing electrons.
Where does the helium used commercially come from?
It comes almost entirely from the natural, slow alpha decay of uranium and thorium in Earth's crust, which accumulates underground and is extracted alongside natural gas.