Copper

Copper, designated by the symbol Cu and atomic number 29, is a chemical element recognized as a ductile, soft, and malleable metal with outstanding thermal and electrical conductivity. When freshly exposed, pure copper exhibits a reddish-orange colour. Copper is part of the d-block in the transition elements and is located in Group 11 of the modern periodic table.

1.0Introduction

Copper is a soft, malleable, and ductile metal with excellent thermal and electrical conductivity. Known for its excellent electrical and thermal conductivity, copper occurs naturally, primarily in minerals like chalcopyrite and bornite, and has been used since around 8000 BCE. Produced by massive stars and found in Earth’s crust, the largest copper mass discovered weighed 420 tonnes. 

The freshly exposed pure copper surface displays a pinkish-orange hue. It is widely used as a conductor of heat and electricity, as a building material, and as a component in various metal alloys, including sterling silver for jewellery, cupronickel for nautical hardware and coins, and constantan for temperature-sensing strain gauges and thermocouples.

Copper is also essential for human health, particularly in the liver, muscles, and bones, where 1.4 – 2.1 mg per kilogram of body weight is typical.

2.0Occurrence and Isotopes of Copper 

Copper is relatively abundant in the Earth's crust, primarily found in minerals like chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), and malachite (Cu₂CO₃(OH)₂), as well as in its native metallic form. It is often extracted from these ores through mining and refining processes.

Copper has two stable isotopes:

1. Copper-63 – Comprising about 69% of naturally occurring copper, it has a relative atomic mass of approximately 62.93 u.
2. Copper-65 makes up around 31% of copper and has a relative atomic mass of about 64.93 u.

These isotopes contribute to the average atomic weight of copper, around 63.55 u. Copper isotopes are also used in scientific research and can provide insights into processes in geology, biology, and industrial applications, especially where tracing copper pathways or sources is essential.

3.0Physical Properties of Copper

4.0Chemical Properties of Copper

Copper’s chemical properties include low reactivity, but it forms compounds like CuSO₄, CuO, CuCl₂, and Cu(NO₃)₂. In the +2 state (Cu²⁺), it erodes with chlorides and acts as a mild oxidiser. Copper commonly appears as Cu⁺ and Cu²⁺, showing green and blue flames, respectively. While resistant to non-oxidizing acids, it reacts with oxidising acids and slowly develops a green protective patina in the air.

1. Oxidation States: Copper exhibits two standard oxidation states, +1 (cuprous) and +2 (cupric). When heated, Cu⁺² gives a green flame, while Cu⁺¹ produces a blue flame.
2. Reaction with Air and Moisture: Copper reacts with air and moisture in the presence of CO2CO_2CO2​, forming a green patina of basic copper carbonate: 2Cu+O₂+CO₂+H₂O→CuCO₃⋅Cu(OH)₂
3. Action of Heat:

Copper forms oxides at different temperatures with oxygen:

• Below 1370 K, copper forms black copper(II) oxide: 2Cu+O₂→2CuO
• Above 1370 K, copper forms red copper(I) oxide: 4Cu+O₂→2Cu₂O

4. Reaction with Acids:

Dilute HCl and H₂SO₄​: Copper requires oxygen (air) to dissolve in dilute hydrochloric and sulfuric acids: 

• 2Cu+4HCl+O₂→2CuCl₂+2H₂O
• 2Cu+2H₂SO₄+O₂→2CuSO₄+2H₂O

Dilute HNO₃​: Reacts to form copper nitrate and release nitric oxide: 

• 3Cu+8HNO₃→3Cu(NO₃)₂+2NO+4H₂O

Concentrated HNO₃​ and H₂SO₄: Forms nitrogen dioxide and sulfur dioxide, respectively:

• Cu+4HNO₃→Cu(NO₃)₂+2NO₂+2H₂O
• Cu+2H₂SO₄→CuSO₄+SO₂+2H₂O

5. Reaction with Halogens: Copper reacts with halogens like fluorine, chlorine, and bromine to form copper(II) halides: Cu+F₂→CuF₂(white)

• Cu+Cl₂→CuCl₂ (yellow-brown)
• Cu+Br₂→CuBr₂ (black)

6. Reaction with Chlorine: Copper reacts directly with chlorine gas to form copper(II) chloride: 

• Cu+Cl₂→CuCl₂

7. Reaction with Alkalis: Copper is resistant to attack by alkalis, maintaining its stability in their presence.
8. Solubility in Acids: Copper does not dissolve in acids that evolve hydrogen unless oxidising agents like nitric or concentrated sulfuric acid are present.

5.0Uses Of Copper

Copper Sulfate:

• Widely used as a poison in agriculture and as an algicide in water purification.

Historical Significance:

• Copper was the first metal worked on in history. The discovery that adding tin could harden it into bronze marked the start of the Bronze Age.

Bronze Production:

• Copper is a critical component in bronze, an alloy combining copper and tin.

Common Products:

• Copper is widely used in a variety of products, including cans, cooking foil, cookware, electrical cables, aircraft, and even space vehicles.

Electrical Conductivity:

• Copper’s excellent electrical conductivity makes it an ideal choice for wiring, with more than half of the world’s copper consumption dedicated to electrical wires.

Chemical Vapor Deposition:

• Copper thin films are applied using chemical vapor deposition, a method widely used in semiconductor production.

Alloying with Gold and Silver:

• Copper is often combined with or coated in gold and silver, serving both decorative and industrial functions.

Primary Uses:

• Electrical Equipment: 60% of copper is used in electrical applications.
• Construction: 20% of copper is used in construction materials.
• Industrial Gear: 15% is used in industrial equipment, including heat exchangers.
• Alloys: 5% of copper usage is in various alloys.

Traditional Alloys:

• Bronze: Copper-tin alloy used historically for tools and weapons.
• Brass: Copper-zinc alloy used in various products.
• Gunmetal: Copper-tin-zinc alloy strong enough for firearms.
• Cupronickel: Copper-nickel alloy commonly used in low-denomination coins.

Advantages for Wiring:

• Copper’s excellent electrical conductivity, ease of handling, and suitability for drawing into thin wires make it perfect for electrical wiring applications.