Calcio (Ca): Bohr Model, Protons, Neutrons & Electrons
Calcio is element number 20, an alkaline earth metal in group 2, period 4. Its atom has 20 protons, 20 neutrons and 20 electrons arranged in 4 shells: 2, 8, 8, 2.
- 20 protons
- 20 neutrons
- 20 electrons
Protons, neutrons and electrons in calcium
El atomic number of calcium is 20, so every calcium atom has 20 protons. A neutral atom has the same number of electrons, 20. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For calcium-40, that is 40 − 20 = 20 neutrons. Calcium has 6 stable isotopes, with 20, 22, 23, 24, 26, 28 neutrons.
How to draw the Bohr model of calcium
- Draw the nucleus and write 20 p⁺ y 20 n⁰ inside it.
- Draw the first shell and put 2 electrons on it (the first shell holds at most 2).
- Draw the second shell and put 8 electrons on it.
- Draw the third shell and put 8 electrons on it.
- Draw the fourth shell and put 2 electrons on it.
- Check: 2 + 8 + 8 + 2 = 20 electrons, the same as the number of protons.
Electron configuration
The electron configuration of calcium is [Ar] 4s². Its 2 outer electrons decide how it reacts: it tends to lose them, forming Ca²⁺ ions.
Key facts about calcium
| Symbol | Ca |
|---|---|
| Atomic number | 20 |
| Relative atomic mass | 40.078 |
| Group · period · block | group 2 · period 4 · s-block |
| Tipo | Metal alcalinotérreo |
| State at 25 °C | solid |
| Capas electrónicas | 2, 8, 8, 2 |
| Electron configuration | [Ar] 4s² |
| Electrones de valencia | 2 |
| Common ion | Ca²⁺ |
| Electronegativity (Pauling) | 1.00 |
| First ionisation energy | 6.11 eV (590 kJ/mol) |
| Atomic radius (empirical) | 180 pm |
¿Dónde calcium sits on the periodic table
Preguntas frecuentes
How many protons, neutrons and electrons does calcium have?
Calcium has 20 protons and 20 electrons (atomic number 20). Its most common isotope, calcium-40, has 40 − 20 = 20 neutrons.
What is the electron configuration of calcium?
[Ar] 4s². In shells that is 2, 8, 8, 2.
How many valence electrons does calcium have?
2. Calcium is in group 2, and its outer shell holds 2 electrons.
Where is calcium on the periodic table?
In group 2, period 4, in the s-block. It is an alkaline earth metal.
