Transition metalElement 29 · d-block

Copper (Cu)

Copper (Cu) is a transition metal with atomic number 29 and a standard atomic weight of 63.546. At room temperature it is a solid that melts at 1,085 °C and boils at 2,560 °C.

29CuCopper63.546

Atomic number

protons

Atomic weight

63.546

CIAAW 2024

Melting point

1,085 °C

1,357.77 K

Boiling point

2,560 °C

2,833.15 K

Density

8.96 g/cm³

near room temperature

Electronegativity

1.9

Pauling scale

State at 25 °C

Solid

Discovered

Prehistoric

Copper at a glance

Identity

Symbol	Cu
Atomic number (Z)	29
Atomic weight	63.546 ± 0.003 (CIAAW 2024)
Category	Transition metal
Group	11
Period	4
Block	d-block
CAS number	7440-50-8

Atomic properties

Electron configuration	[Ar] 3d¹⁰ 4s¹ Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹
Electrons per shell	2, 8, 18, 1
Oxidation states	+2 Less common: -2, 0, +1, +3, +4
Electronegativity (Pauling)	1.9
First ionisation energy	7.726 eV (745.5 kJ/mol) 2nd: 20.292 eV · 3rd: 36.841 eV
Electron affinity	1.235 eV
Atomic radius (empirical)	135 pm
Covalent radius	112 pm
Van der Waals radius	196 pm

Physical properties

State at 25 °C	Solid
Melting point	1,084.6 °C · 1,984.3 °F · 1,357.77 K
Boiling point	2,560 °C · 4,640 °F · 2,833.15 K
Density	8.96 g/cm³
Specific heat capacity	0.385 J/(g·K)
Thermal conductivity	401 W/(m·K)
Crystal structure	Face-centred cubic

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	⁶³Cu 69.15%, ⁶⁵Cu 30.85%
Stable isotopes	6
Known isotopes	33
Abundance in Earth's crust	60 mg/kg
Abundance in seawater	0.00025 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Copper electron configuration

Copper has 29 electrons. Written in short form, its ground-state configuration is [Ar] 3d¹⁰ 4s¹ — the electrons of the noble gas argon, plus 3d¹⁰ 4s¹.Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹.

An exception to the filling rule. The simple aufbau (Madelung) order predicts 4s², 3d⁹, but copper actually has 4s¹, 3d¹⁰. Half-filled and filled subshells, and the close energies of the outer orbitals, make this arrangement more stable.

3d↑↓↑↓↑↓↑↓↑↓

4s↑

Discovery and name

Discovered

Prehistoric — Known since antiquity.

Name

Latin cuprum, from Cyprus, an ancient source.

Known for

An excellent conductor of electricity used in wiring, motors and electronics. One of the first metals humans worked; bronze and brass are copper alloys.

Isotopes of copper

Naturally occurring copper is a mix of 2 isotopes. Each has 29 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
⁶³Cu	29	34	69.15%	stable
⁶⁵Cu	29	36	30.85%	stable

33 isotopes of copper are known in our data set (half-lives as published in nuclear data tables).

Copper compared with group 11

The other elements in group 11, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Copper	29	63.546	1,085 °C	2,560 °C	8.96 g/cm³	1.9
Silver	47	107.87	962 °C	2,162 °C	10.5 g/cm³	1.93
Gold	79	196.97	1,064 °C	2,836 °C	19.3 g/cm³	2.54
Roentgenium	111	[282]	—	—	28.7 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of copper?

The standard atomic weight of copper is 63.546 ± 0.003 (CIAAW 2024), so one mole weighs about 63.546 grams.

How many protons, neutrons and electrons does copper have?

A neutral copper atom has 29 protons and 29 electrons. Its most common isotope, copper-63, has 34 neutrons.

What is the electron configuration of copper?

[Ar] 3d¹⁰ 4s¹ (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹).

What are the melting and boiling points of copper?

Copper melts at 1,084.62 °C (1,984.3 °F) and boils at 2,560 °C (4,640 °F).

Is copper a metal?

Copper is a metal. It is in group 11, period 4, and is a solid at room temperature.

Who discovered copper?

Copper has been known since ancient times.