Copper (Cu): Bohr Model, Protons, Neutrons & Electrons
Copper is element number 29, a transition metal in group 11, period 4. Its atom has 29 protons, 34 neutrons and 29 electrons arranged in 4 shells: 2, 8, 18, 1.
Protons, neutrons and electrons in copper
The atomic number of copper is 29, so every copper atom has 29 protons. A neutral atom has the same number of electrons, 29. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For copper-63, that is 63 − 29 = 34 neutrons. Copper has 2 stable isotopes, with 34, 36 neutrons.
How to draw the Bohr model of copper
- Draw the nucleus and write 29 p⁺ and 34 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 1 electron on it.
- Check: 2 + 8 + 18 + 1 = 29 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, 1) is the one to draw.
Electron configuration
The electron configuration of copper is [Ar] 4s¹ 3d¹⁰. As a transition metal it fills an inner d-subshell, and its common ion is Cu²⁺.
Key facts about copper
| Symbol | Cu |
|---|---|
| Atomic number | 29 |
| Relative atomic mass | 63.546 |
| Group · period · block | group 11 · period 4 · d-block |
| Type | Transition Metal |
| State at 25 °C | solid |
| Electron shells | 2, 8, 18, 1 |
| Electron configuration | [Ar] 4s¹ 3d¹⁰ |
| Valence electrons | varies (outer shell: 1) |
| Common ion | Cu²⁺ |
| Electronegativity (Pauling) | 1.90 |
| First ionisation energy | 7.73 eV (746 kJ/mol) |
| Atomic radius (empirical) | 135 pm |
Where copper sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does copper have?
Copper has 29 protons and 29 electrons (atomic number 29). Its most common isotope, copper-63, has 63 − 29 = 34 neutrons.
What is the electron configuration of copper?
[Ar] 4s¹ 3d¹⁰. In shells that is 2, 8, 18, 1.
How many valence electrons does copper have?
Copper is a transition metal, so its valence electrons are spread over two shells; its outermost shell holds 1.
Where is copper on the periodic table?
In group 11, period 4, in the d-block. It is a transition metal.
