Copper (Cu): electron configuration, atomic mass and facts
Copper (Cu) is element 29 of the periodic table, a transition metal in period 4, group 11. Its electron configuration is [Ar] 3d10 4s1, with electrons arranged in shells 2, 8, 18, 1, and its standard atomic weight is 63.546 u.
💡 An excellent conductor used in almost every electric wire. Its compounds turn flames blue-green.
▶ Watch Copper’s electrons orbit in the interactive periodic tableCopper at a glance
| Symbol | Cu |
|---|---|
| Atomic number | 29 |
| Atomic mass | 63.546 u |
| Category | Transition metal |
| Group | 11 |
| Period | 4 |
| Block | d-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s1 |
| Noble-gas shorthand | [Ar] 3d10 4s1 |
| Electrons per shell | 2, 8, 18, 1 |
| Electronegativity (Pauling) | 1.9 |
| State at 20 °C | solid |
| Flame test colour | blue-green |
Experiments with copper
🔩 Iron nail in copper sulfate
A more reactive metal displaces copper: the nail turns pink and the blue fades to green.
🌳 Silver tree
Copper wire in silver nitrate grows a sparkling tree of silver crystals.
💙 Copper–ammonia complex
Ammonia first gives pale-blue Cu(OH)₂, then a stunning deep-blue complex.
Where is Copper on the periodic table?
Copper is in period 4, group 11, in the d-block. The period number matches its 4 electron shells, and the block names the subshell its last electrons fill. In the same group, Silver sits directly below it. Elements in the same column of the d-block often have similar chemistry.
How to work out the electron configuration of Copper
Put 29 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d⁹ (29). Copper is one of the exceptions to this filling order: experiments show its ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰ rather than 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹, because the neighbouring subshells are so close in energy and a half-filled or completely filled d subshell is extra stable. In shorthand, [Ar] stands for the 18 electrons of argon, giving [Ar] 3d¹⁰ 4s¹.
How electronegative is Copper?
Copper has a Pauling electronegativity of 1.9, ranking 37 of the 100 elements with a known value (fluorine is highest at 3.98). That is in the middle of the range.
Copper in the virtual lab
Faradium’s chemistry workbench includes these chemicals that contain copper: Copper turnings, Copper sulfate crystals, Anhydrous copper sulfate, Copper(II) oxide, Malachite, Copper(II) sulfate, Copper(II) chloride. Open the Chemistry Lab to experiment with them.
Frequently asked questions
What is the electron configuration of Copper?
The electron configuration of Copper (Cu) is 1s2 2s2 2p6 3s2 3p6 3d10 4s1. In noble-gas shorthand it is written [Ar] 3d10 4s1.
How many electrons does Copper have in each shell?
Copper has 29 electrons arranged in shells as 2, 8, 18, 1.
What is the atomic mass of Copper?
The standard atomic weight of Copper is 63.546 u, so one mole of Copper atoms has a mass of about 63.546 g.
Is Copper a metal?
Yes. Copper is a transition metal.
Explore nearby elements
More transition metals: Chromium, Manganese, Iron, Cobalt, Nickel, Zinc. See all elements on the periodic table.