Ba
Alkaline earth metal
Barium
Z 56A 137mass 137.33
Atomic model
tap a particleEvery nucleon is drawn individually — 56 protons and 81 neutrons packed into the nucleus, with 56 electrons on shells outside.
56+1
Protons
Set the element — change this and it becomes a different atom.
810
Neutrons
Change only these and you get a different isotope of the same element.
56−1
Electrons
Sit outside the nucleus and decide the chemistry, not the element.
Element data
- Nucleons
- 137 (56 p + 81 n)
- Electron shells
- 2 · 8 · 18 · 18 · 8 · 2
- Valence shell
- 2 electrons
- Atomic mass
- 137.33 u
Stability
Barium has no measured radioactive isotope in this lab — its nuclei are stable, so decay must be shown as an illustration.
Open the decay lab