Copper (Cu)
Copper is element 29, a transition metal in group 11, period 4. A neutral atom has 29 protons, 35 neutrons and 29 electrons, 1 of them valence electrons.
Transition metal- Atomic number
- 29
- Atomic mass
- 63.55 u
- Valence electrons
- 1*
- Protons · neutrons
- 29 · 35
- Electrons per shell
- 2, 8, 18, 1
- At room temperature
- solid
Bohr model of copper
The Bohr model draws copper as a nucleus of 29 protons and 35 neutrons, with its 29 electrons on 4 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 1 in shell 4. Press Build the atom to watch the shells fill from the inside out. The outer ring (the N shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of copper
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
Short form (noble gas notation): [Ar] 4s¹ 3d¹⁰. The [Ar] stands for the electrons of argon, the noble gas before it.
Copper breaks the usual filling order. The Aufbau rule predicts 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹, but experiments show the configuration above. Moving one electron from the s subshell gives a half-full or full d subshell, which is more stable.
How many valence electrons does copper have?
Copper has 1 valence electron.
Copper is a transition metal, so its valence electrons are less clear-cut than for main-group elements. It has 1 electron in its outermost shell (shell 4), and electrons in its inner d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 29 | equal to the atomic number |
|---|---|---|
| Electrons | 29 | equal to the protons in a neutral atom |
| Neutrons | 35 | mass number 64 − 29 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Copper properties
| Symbol | Cu |
|---|---|
| Category | Transition metal |
| Group · period · block | 11 · 4 · d |
| Atomic mass | 63.55 u |
| State at 25 °C | solid |
| Melting point | 1,358 K (1,080 °C, 1,980 °F) |
| Boiling point | 2,835 K (2,560 °C, 4,640 °F) |
| Density | 8.933 g/cm³ |
| Electronegativity (Pauling) | 1.9 |
| Atomic radius | 140 pm |
| First ionization energy | 7.726 eV |
| Electron affinity | 1.228 eV |
| Oxidation states | +2, +1 |
| Common ion charge | +2, +1 |
| Discovered | Known since ancient times |
Where copper sits on the periodic table
Group 11: Silver, Gold, Roentgenium.
Questions about copper
How many valence electrons does copper have?
Copper has 1 valence electron in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does copper have?
A neutral copper atom has 29 protons and 29 electrons. Its most common form has about 35 neutrons (mass number 64 − 29 protons).
What is the electron configuration of copper?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰, written in short form as [Ar] 4s¹ 3d¹⁰.
What does the Bohr model of copper look like?
A nucleus of 29 protons and 35 neutrons, circled by 4 electron shells holding 2, 8, 18, 1 electrons.
What is the atomic number of copper?
29. The atomic number is the number of protons in the nucleus, and it is what makes an atom copper.