Helium Element Properties
Complete reference for Helium (He, element 2): atomic data, electron configuration, isotopes, physical constants, and chemical behavior.
Helium
Noble Gas — Period 1, Group 18
Atomic Identity
Electron Configuration
No unpaired electrons
Isotopes of Helium
| Isotope | Symbol | Protons | Neutrons | Mass (u) | Natural Abundance | Stability |
|---|---|---|---|---|---|---|
| Helium-3 | ³He | 2 | 1 | 3.01602932265 | 0.000134% | Stable |
| Helium-4 | ⁴He | 2 | 2 | 4.00260325413 | 99.999866% | Stable |
| Helium-6 | ⁶He | 2 | 4 | 6.01888589 | Radioactive |
Unstable
β⁻ decay, t½ = 806.7 ms |
| Helium-8 | ⁸He | 2 | 6 | 8.03393439 | Radioactive |
Unstable
β⁻ decay, t½ = 119.1 ms |
Physical Properties
Chemical Properties
Ground State Quantum Numbers
Notable Emission Lines
These lines were first observed in the solar spectrum in 1868, leading to helium’s discovery before it was found on Earth.
Key Facts About Helium
Second Most Abundant
Helium is the second most abundant element in the universe (~24% by mass), but extremely rare on Earth where it escapes into space.
Lowest Boiling Point
At 4.22 K (−268.93 °C), helium has the lowest boiling point of any element and is the only substance that does not solidify at normal pressure.
Superfluid Helium-4
Below 2.17 K, liquid ⁴He becomes a superfluid with zero viscosity, flowing through microscopic pores and climbing container walls spontaneously.
MRI & Cryogenics
Liquid helium cools the superconducting magnets in MRI machines to near absolute zero, enabling strong magnetic fields without electrical resistance.
Solar Origin
Helium was discovered in 1868 from solar spectral lines before ever being found on Earth. Its name comes from Helios, the Greek god of the Sun.
Fusion Product
Helium-4 is produced in stars by hydrogen fusion and in Earth's crust by alpha decay of radioactive elements such as uranium and thorium.
Summary
Complete reference for Helium (He, element 2): atomic data, electron configuration, isotopes, physical constants, and chemical behavior.
How it works
- Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
- Check the electron configuration panel for orbital notation and quantum numbers.
- Review the isotopes table for helium-3 and helium-4 data including natural abundance.
- Consult the physical properties panel for boiling point, density, and state at STP.
- Use the chemical properties section to understand the noble gas behavior and ionization energies.
- Copy any value with one click for use in reports or calculations.
Use cases
- Look up helium constants for chemistry homework or exams.
- Verify atomic data when writing lab reports.
- Reference isotope masses for nuclear chemistry or cryogenics calculations.
- Check thermodynamic constants for low-temperature physics or engineering.
- Teach or learn noble gas properties starting with the lightest noble gas.
- Confirm electron configuration before writing molecular orbital diagrams.
- Compare helium-3 and helium-4 properties for quantum fluid research.
- Quick-reference ionization energy for spectroscopy or plasma physics work.