He
Noble gas
Helium
Z 2A 4mass 4.003
Atomic model
tap a particleEvery nucleon is drawn individually — 2 protons and 2 neutrons packed into the nucleus, with 2 electrons on shells outside.
2+1
Protons
Set the element — change this and it becomes a different atom.
20
Neutrons
Change only these and you get a different isotope of the same element.
2−1
Electrons
Sit outside the nucleus and decide the chemistry, not the element.
Element data
- Nucleons
- 4 (2 p + 2 n)
- Electron shells
- 2
- Valence shell
- 2 electrons
- Atomic mass
- 4.003 u
Stability
Helium has no measured radioactive isotope in this lab — its nuclei are stable, so decay must be shown as an illustration.
Open the decay lab