Atomic number 2
Helium
Noble gas
In the real world
Quick facts
- Atomic mass
- 4.003
- Group
- 18
- Period
- 1
- State (STP)
- gas
- Electronegativity
- –
- Common ox. states
- 0
Properties
Electron configuration
1s²
- Ionization energy
- 2372.3 kJ/mol
- Electron affinity
- -50.0 kJ/mol
- Melting point
- –
- Boiling point
- 4.22 K (-268.9 °C)
How dangerous is it?
2/5 · Caution
Completely non-toxic and unreactive, but in a sealed room it can quietly push out the air you need to breathe.
- Asphyxiant
It is not poisonous; it is dangerous only because it can crowd out oxygen in a closed space, with no warning. (the danger is the room, not the gas itself)
Used with good ventilation; sealed tanks and rooms are checked with an oxygen monitor.
How it bonds
Helium has a closed 1s² shell and the highest first ionization energy of any element. It forms no stable compounds at normal conditions - what you see is what it is. Two atoms in a balloon never link up.
Where you meet it
- Periodic Quest challengeunlock card
