Ca
Alkaline earth metal
Calcium
Z 20A 40mass 40.078
Atomic model
tap a particleEvery nucleon is drawn individually — 20 protons and 20 neutrons packed into the nucleus, with 20 electrons on shells outside.
20+1
Protons
Set the element — change this and it becomes a different atom.
200
Neutrons
Change only these and you get a different isotope of the same element.
20−1
Electrons
Sit outside the nucleus and decide the chemistry, not the element.
Element data
- Nucleons
- 40 (20 p + 20 n)
- Electron shells
- 2 · 8 · 8 · 2
- Valence shell
- 2 electrons
- Atomic mass
- 40.078 u
Stability
Calcium has no measured radioactive isotope in this lab — its nuclei are stable, so decay must be shown as an illustration.
Open the decay lab