Cadmium (Cd): Bohr Model, Protons, Neutrons & Electrons
Cadmium is element number 48, a transition metal in group 12, period 5. Its atom has 48 protons, 66 neutrons and 48 electrons arranged in 5 shells: 2, 8, 18, 18, 2.
Protons, neutrons and electrons in cadmium
The atomic number of cadmium is 48, so every cadmium atom has 48 protons. A neutral atom has the same number of electrons, 48. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For cadmium-114, that is 114 − 48 = 66 neutrons. Cadmium has 8 stable isotopes, with 58, 60, 62, 63, 64, 65, 66, 68 neutrons.
How to draw the Bohr model of cadmium
- Draw the nucleus and write 48 p⁺ and 66 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 18 electrons on it.
- Draw the fourth shell and put 18 electrons on it.
- Draw the fifth shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 18 + 2 = 48 electrons, the same as the number of protons.
From potassium onwards the shells don’t simply fill as 2, 8, 8: the fourth shell starts before the third is full, so the real arrangement above (2, 8, 18, 18, 2) is the one to draw.
Electron configuration
The electron configuration of cadmium is [Kr] 5s² 4d¹⁰. As a transition metal it fills an inner d-subshell, and its common ion is Cd²⁺.
Key facts about cadmium
| Symbol | Cd |
|---|---|
| Atomic number | 48 |
| Relative atomic mass | 112.41 |
| Group · period · block | group 12 · period 5 · d-block |
| Type | Transition Metal |
| State at 25 °C | solid |
| Electron shells | 2, 8, 18, 18, 2 |
| Electron configuration | [Kr] 5s² 4d¹⁰ |
| Valence electrons | varies (outer shell: 2) |
| Common ion | Cd²⁺ |
| Electronegativity (Pauling) | 1.69 |
| First ionisation energy | 8.99 eV (867 kJ/mol) |
| Atomic radius (empirical) | 155 pm |
Where cadmium sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does cadmium have?
Cadmium has 48 protons and 48 electrons (atomic number 48). Its most common isotope, cadmium-114, has 114 − 48 = 66 neutrons.
What is the electron configuration of cadmium?
[Kr] 5s² 4d¹⁰. In shells that is 2, 8, 18, 18, 2.
How many valence electrons does cadmium have?
Cadmium is a transition metal, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is cadmium on the periodic table?
In group 12, period 5, in the d-block. It is a transition metal.
