Helium (He): Electron Configuration, Properties and Uses
Helium (He): Electron Configuration, Properties and Uses
Electron configuration 1s2 · group 18 · period 1 · Ar 4.0026
Helium data
- Atomic number
- 2
- Relative atomic mass
- 4.0026
- Group
- 18
- Period
- 1
- Block
- s
- Category
- Noble gas
- Electron configuration
- 1s2
- Full configuration
- 1s2
- Electrons per shell
- 2 (K)
- Valence electrons
- 2
- Electronegativity (Pauling)
- no data
- First ionisation energy
- 24.587 eV
- Atomic radius (van der Waals)
- 140 pm
- State at room temperature
- Gas
- Melting point
- −272 °C (under high pressure)
- Boiling point
- −269 °C
- Density
- 0.1785 g/L (0 °C, 1 atm)
- Common oxidation states
- 0
- Discovered
- 1868
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2
Orbital diagram (outer electrons)
About helium
Helium, symbol He, is element number 2 in the periodic table. It is a noble gas in group 18, period 1, s-block. Helium was first discovered in 1868. At room temperature helium is a gas that is lighter than air (0.1785 g/L) and liquefies at −269 °C.
Helium electron configuration
The electron configuration of helium is 1s2. Its electrons occupy 1 shell: K = 2. Helium has only 2 electrons and a full K shell, so it is placed with the noble gases even though it is s-block.
Filling order: 1s2(2)
Uses of helium
Well-known applications of helium include cooling MRI magnets as liquid helium, as a carrier gas in gas chromatography, filling balloons and shielding welds.
Safety
Helium is non-toxic and almost unreactive, but large amounts in a closed room can displace oxygen. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 18
Frequently asked questions
What is the electron configuration of helium?
The electron configuration of helium (He, atomic number 2) is 1s2. By shell: 2.
How many valence electrons does helium have?
Helium has 2 valence electrons.
Which group and period is helium in?
Helium is in group 18, period 1, s-block.
What is the atomic mass of helium?
The relative atomic mass of helium is 4.0026. Use it to calculate molar mass with the molar mass calculator.
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