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Revision Guide • Class 10-12 / JEE / NEET

Copper (Cu): Properties, Reactions & Applications (JEE/NEET/CBSE Revision)

By Periodic Table India
CBSE / JEE Prep Notes
Copper d-block elements Transition Metals JEE Chemistry NEET Chemistry CBSE Class 12 Inorganic Chemistry

Introduction to Copper (Cu)

Copper (Cu), a transition metal, has been pivotal throughout human history, from ancient tools and coinage to modern electrical wiring and electronics. Its unique combination of high electrical and thermal conductivity, malleability, ductility, and corrosion resistance makes it indispensable in numerous applications.

CBSE/JEE Quick Revision Notes

  • Symbol: Cu
  • Atomic Number: 29
  • Atomic Mass: 63.55 g/mol
  • Electronic Configuration: [Ar] 3d^10 4s^1 (An exception to the Aufbau principle due to the stability of a fully filled d-subshell)
  • Group: 11 (or IB)
  • Period: 4
  • Block: d-block (Transition Metal)
  • Common Oxidation States: +1 (cuprous) and +2 (cupric). The +2 state is generally more stable in aqueous solutions.
  • Nature: Reddish-brown metal, highly malleable and ductile. Excellent conductor of heat and electricity. Paramagnetic in the Cu^2+ state due to one unpaired electron in 3d^9 configuration.

Electron Configuration & Bonding Behavior

Copper exhibits an anomalous electron configuration of [Ar] 3d^10 4s^1 rather than the expected [Ar] 3d^9 4s^2. This is attributed to the enhanced stability of completely filled (d^10) and half-filled (d^5) d-orbitals.

  • Cu^+ ion (Cuprous): Formed by the loss of the 4s^1 electron, resulting in [Ar] 3d^10. It is diamagnetic and generally less stable in aqueous solution, tending to disproportionate into Cu^2+ and Cu. 2Cu^+(aq) → Cu^2+(aq) + Cu(s)
  • Cu^2+ ion (Cupric): Formed by the loss of the 4s^1 electron and one 3d electron, resulting in [Ar] 3d^9. It is paramagnetic due to one unpaired electron and typically gives blue solutions and compounds. This is the more stable oxidation state in aqueous environments.

Copper forms a variety of compounds, including ionic salts (e.g., CuCl2), covalent compounds, and numerous coordination complexes due to the availability of d-orbitals for ligand interaction.

Crucial Chemical Reactions

1. Reaction with Air/Oxygen

  • At Room Temperature: Copper tarnishes slowly in moist air due to the formation of basic copper carbonate (verdigris). 2Cu(s) + H2O(l) + CO2(g) + O2(g) → CuCO3·Cu(OH)2(s)
  • On Heating (Strongly) in Air: Forms black copper(II) oxide. 2Cu(s) + O2(g) → 2CuO(s)
  • At High Temperatures (Limited Oxygen/with excess Cu): Forms red copper(I) oxide. 4Cu(s) + O2(g) → 2Cu2O(s)

2. Reaction with Acids

Copper is less reactive than hydrogen and does not react with non-oxidizing acids like dilute HCl or H2SO4. However, it reacts with oxidizing acids.

  • With Dilute Nitric Acid: Produces nitric oxide gas. 3Cu(s) + 8HNO3(dilute) → 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l)
  • With Concentrated Nitric Acid: Produces nitrogen dioxide gas. Cu(s) + 4HNO3(conc) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)
  • With Hot, Concentrated Sulfuric Acid: Produces sulfur dioxide gas. Cu(s) + 2H2SO4(conc, hot) → CuSO4(aq) + SO2(g) + 2H2O(l)

3. Reaction with Halogens

  • Copper reacts with halogens to form copper(II) halides. Cu(s) + Cl2(g) → CuCl2(s) Cu(s) + Br2(l) → CuBr2(s)

4. Displacement Reactions

Copper can displace less reactive metals from their salt solutions.

  • Displacement of Silver: Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

5. Complex Formation

Copper(II) ions form characteristic deep blue solutions with ammonia due to the formation of tetraamminecopper(II) ion.

  • CuSO4(aq) + 4NH3(aq) → [Cu(NH3)4]SO4(aq)

Industrial and Biological Importance

Industrial Importance

  • Electrical Industry: Copper’s high electrical conductivity makes it the primary material for electrical wiring, cables, and components.
  • Alloys: Essential component in numerous alloys:
    • Brass: (Copper + Zinc) - used in plumbing, musical instruments, decorative items.
    • Bronze: (Copper + Tin) - used in sculptures, bearings, marine fittings.
    • German Silver: (Copper + Zinc + Nickel) - used in cutlery, jewellery.
  • Construction: Used in roofing, plumbing, and architectural applications due to its durability and corrosion resistance.
  • Coinage: Historically and currently used in coins.
  • Catalysis: Copper and its compounds serve as catalysts in various organic reactions, such as the synthesis of phthalocyanine dyes.

Biological Importance

  • Essential Trace Element: Copper is vital for all living organisms, required in small amounts.
  • Enzyme Cofactor: It is a key component of many enzymes, including:
    • Cytochrome c oxidase: Involved in cellular respiration.
    • Superoxide dismutase (SOD): An antioxidant enzyme protecting cells from damage.
    • Tyrosinase: Involved in melanin production.
    • Lysyl oxidase: Essential for collagen and elastin cross-linking (connective tissue formation).
  • Oxygen Transport: In some mollusks and arthropods, copper-containing protein Hemocyanin acts as an oxygen carrier, analogous to hemoglobin in vertebrates.
  • Iron Metabolism: Plays a crucial role in iron absorption, transport, and utilization.
  • Health Implications: Both copper deficiency and excess can lead to serious health issues.
    • Wilson’s disease: Genetic disorder leading to excessive copper accumulation in the liver, brain, and other organs.
    • Menkes disease: Genetic disorder leading to copper deficiency.
Cu

Copper (Cu)

Atomic Number 29

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