Se
Reactive nonmetal
Selenium
Z 34A 79mass 78.971
Atomic model
tap a particleEvery nucleon is drawn individually — 34 protons and 45 neutrons packed into the nucleus, with 34 electrons on shells outside.
34+1
Protons
Set the element — change this and it becomes a different atom.
450
Neutrons
Change only these and you get a different isotope of the same element.
34−1
Electrons
Sit outside the nucleus and decide the chemistry, not the element.
Element data
- Nucleons
- 79 (34 p + 45 n)
- Electron shells
- 2 · 8 · 18 · 6
- Valence shell
- 6 electrons
- Atomic mass
- 78.971 u
Stability
Selenium has no measured radioactive isotope in this lab — its nuclei are stable, so decay must be shown as an illustration.
Open the decay lab