2HeHelium4.00260221s²
noble gas
Helium
Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
Electrons by shell
Electron configuration
1s2
At a glance
- Atomic number
- 2
- Atomic mass
- 4.002602 u
- Phase
- Gas
- Density
- 0.1786 g/L
- Melting point
- 0.95 K
- Boiling point
- 4.222 K
- First ionization energy
- 2,372.3 kJ/mol
- Electronegativity
- Unavailable
- Electron affinity
- -48 kJ/mol
- Molar heat capacity
- Unavailable
- Period
- 1
- Appearance
- colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.