Ar
Noble gas
Argon
Z 18A 40mass 39.948
Atomic model
tap a particleEvery nucleon is drawn individually — 18 protons and 22 neutrons packed into the nucleus, with 18 electrons on shells outside.
18+1
Protons
Set the element — change this and it becomes a different atom.
220
Neutrons
Change only these and you get a different isotope of the same element.
18−1
Electrons
Sit outside the nucleus and decide the chemistry, not the element.
Element data
- Nucleons
- 40 (18 p + 22 n)
- Electron shells
- 2 · 8 · 8
- Valence shell
- 8 electrons
- Atomic mass
- 39.948 u
Stability
Argon has no measured radioactive isotope in this lab — its nuclei are stable, so decay must be shown as an illustration.
Open the decay lab