He
4.003Helium
Helyum
Helium is a very light noble gas with a full first electron shell. It is chemically inert, nonflammable, and important in cryogenics, balloons, leak detection and scientific instruments.
2
4.0026 g/mol
1s²
2
—
1.64e-4 g/cm³
-272.0 °C
-268.9 °C
Pierre Janssen
Helium was first detected in 1868 as an unknown yellow spectral line in sunlight during a solar eclipse. It was later isolated on Earth from uranium minerals by Sir William Ramsay in 1895.
Helium-3
Natural abundance: 0.000137%. Rare isotope used in neutron detection and low-temperature research.Helium-4
Natural abundance: 99.99986%. The dominant helium isotope; equivalent to an alpha particle nucleus.HeH⁺
Helium Hydride IonOne of the first molecular ions expected in the early universe.- Balloons and airships because it is nonflammable
- Liquid helium cooling for MRI superconducting magnets
- Heliox breathing mixtures for deep diving and medical use
- Leak detection due to its small atomic size
- Low-temperature physics and cryogenic research
Helium has no known biological role. Because it is inert, it can be mixed with oxygen for specialized breathing gases used in deep-sea diving.
- Helium has the lowest boiling point of any element.
- At normal pressure helium does not solidify, even near absolute zero.
- Helium-4 becomes a superfluid below about 2.17 K, allowing it to flow with nearly zero viscosity.
- Most helium on Earth is produced by radioactive alpha decay and accumulates in natural gas deposits.
- Inhaling helium raises voice pitch because sound travels faster in helium than in air.
- Helium is in group 18 and is classified as a noble gas.
- Its electron configuration is 1s², a full first shell.
- Helium is chemically inert because removing or sharing its electrons requires very high energy.
What is the atomic number of helium?
The atomic number of helium is 2.
What is the electron configuration of helium?
Helium has the electron configuration 1s².
Why is helium a noble gas?
Helium has a filled first electron shell, which makes it extremely unreactive.
What is superfluid helium?
Helium-4 becomes a superfluid below about 2.17 K, where it can flow with nearly zero viscosity.
What is helium used for?
Helium is used in balloons, MRI cooling, leak detection, heliox breathing mixtures and cryogenic research.