---
title: "Copper (Cu) — element 29"
description: "Copper is element 29, symbol Cu, atomic weight 63.546. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/copper/
site: "At One Place"
---

# Copper (Cu)

**Copper — element 29: Cu**

63.546 u · Transition metal · period 4, group 11

Copper is the second-best electrical conductor of any metal after silver, and silver is too expensive to wire a house with, so almost all electricity that has ever flowed has flowed through copper. It kills bacteria on contact — a mechanism called contact killing, in which copper ions rupture the cell membrane — so brass door handles in a hospital genuinely stay cleaner than stainless ones. Its configuration is anomalous: [Ar] 4s¹ 3d¹⁰, because a completely filled d subshell is worth borrowing an electron from the 4s shell for.

## Properties

- **Atomic number:** 29
- **Symbol:** Cu
- **Standard atomic weight:** 63.546 u
- **Category:** Transition metal
- **Group:** 11
- **Period:** 4
- **Block:** d-block
- **Electron configuration:** [Ar] 4s¹ 3d¹⁰
- **Electrons per shell:** 2, 8, 18, 1
- **Melting point:** 1,357.77 K — 1084.6 °C — 1984.3 °F
- **Boiling point:** 2,835 K — 2561.8 °C — 4643.3 °F
- **Density:** 8.933 g/cm³
- **Electronegativity:** 1.9 (Pauling)
- **Oxidation states:** +2, +1
- **Discovered:** Known since antiquity

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
- **Noble gas shorthand:** [Ar] 4s¹ 3d¹⁰
- **Shells:** K: 2 · L: 8 · M: 18 · N: 1

## What it is used for

- Electrical wiring, motor windings and busbars
- Domestic water pipe and heating systems
- Roofing and cladding, where it weathers to green
- Brass and bronze, its two ancient alloys
- Antimicrobial touch surfaces in hospitals

> Anomalous electron configuration: [Ar] 4s¹ 3d¹⁰ rather than the predicted 4s² 3d⁹. The green of weathered copper is a carbonate and sulfate patina, not the red-brown oxide, and it protects the metal underneath — the Statue of Liberty's skin is only about 2.4 mm thick.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 27 | Cobalt | Co | 58.933 |
| 28 | Nickel | Ni | 58.693 |
| 29 | Copper ← | Cu | 63.546 |
| 30 | Zinc | Zn | 65.38 |
| 31 | Gallium | Ga | 69.723 |

## Group 11

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Copper sits in group 11 with silver, gold, roentgenium.

## Common questions

### What is the atomic number of copper?

29. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for copper?

Cu.

### What is the electron configuration of copper?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰, or [Ar] 4s¹ 3d¹⁰ in noble-gas shorthand.

### What is the melting point of copper?

1,357.77 K — 1084.6 °C — 1984.3 °F

## Related pages

- [Cobalt (Co)](https://atoneplace.net/element/cobalt/)
- [Nickel (Ni)](https://atoneplace.net/element/nickel/)
- [Zinc (Zn)](https://atoneplace.net/element/zinc/)
- [Gallium (Ga)](https://atoneplace.net/element/gallium/)
- [Silver (Ag)](https://atoneplace.net/element/silver/)
- [Gold (Au)](https://atoneplace.net/element/gold/)
- [Roentgenium (Rg)](https://atoneplace.net/element/roentgenium/)

## Sources

- Official vendor product documentation — At One Place (/about/)