Pa
Actinide
Protactinium
Z 91A 231mass 231.04
Atomic model
tap a particleEvery nucleon is drawn individually — 91 protons and 140 neutrons packed into the nucleus, with 91 electrons on shells outside.
91+1
Protons
Set the element — change this and it becomes a different atom.
1400
Neutrons
Change only these and you get a different isotope of the same element.
91−1
Electrons
Sit outside the nucleus and decide the chemistry, not the element.
Element data
- Nucleons
- 231 (91 p + 140 n)
- Electron shells
- 2 · 8 · 18 · 32 · 21 · 8 · 2
- Valence shell
- 2 electrons
- Atomic mass
- 231.04 u
Stability
Protactinium has no measured radioactive isotope in this lab — its nuclei are stable, so decay must be shown as an illustration.
Open the decay lab