Element 2
Helium
Noble gases
Helium (He) is in the s-block of the periodic table — group 18, period 1.
Helium is a chemical element with symbol He and atomic number 2.
Key data
- Atomic number
- 2
- Atomic mass
- 4.003 u
- Group / Period
- 18 / 1
- Block
- s-block
- Phase at STP
- Gas
- Density
- 0.1786 g/cm³
- Melting point
- -272.2 °C
- Boiling point
- -268.9 °C
- Electron configuration
- 1s2
Periodic table block
Helium is in the s-block (group 18, period 1). Elements land in the s-block when their highest-energy electrons fill an s subshell — this includes hydrogen, helium, and the reactive metals on the far left of the table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Cryogenics for MRI
- •Party balloons
- •Welding shield gas
Discovery
Year: 1895
Discovered by: Pierre Janssen
Frequently asked questions
What is the atomic number of Helium?
Helium has atomic number 2. Its symbol is He and its atomic mass is 4.003 u.
What category of element is Helium?
Helium is classified as noble gases. It sits in group 18, period 1 of the periodic table.
What block of the periodic table is Helium in?
Helium is in the s-block (group 18, period 1). Its highest-energy electrons occupy the s subshell — you can see this in its electron configuration, 1s2.
What is Helium used for?
Common uses of Helium include: Cryogenics for MRI, Party balloons, Welding shield gas.
When was Helium discovered?
Helium was discovered in 1895 by Pierre Janssen.
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