Copper
The metal and its alloys have been used for thousands of years. In the Roman era, copper was principally mined on Cyprus, hence the origin of the name of the metal as сyprium (metal of Cyprus), later shortened to сuprum. Its compounds are commonly encountered as copper(II) salts, which often impart blue or green colors to minerals such as azurite and turquoise and have been widely used historically as pigments. Architectural structures built with copper corrode to give green verdigris (or patina). Decorative art prominently features copper, both by itself and as part of pigments.
Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustacea copper is a constituent of the blood pigment hemocyanin, which is replaced by the iron-complexed hemoglobin in fish and other vertebrates. The main areas where copper is found in vertebrate animals are liver, muscle and bone.[citation needed] In sufficient concentration, copper compounds are poisonous to higher organisms and are used as bacteriostatic substances, fungicides, and wood preservatives.
Occurrence
Copper is synthesized in massive stars and is present in the Earth's crust at a concentration of about 50 parts per million (ppm), where it occurs as native copper or in minerals such as the copper sulfides chalcopyrite and chalcocite, copper carbonates azurite and malachite and the copper(I) oxide mineral cuprite. The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal, with the largest described single crystal measuring 4.4×3.2×3.2 cm.
| Symbol | Cu | |
| Atomic Number | 29 | |
| Atomic Weight | 63.546 | |
| Oxidation States | +1,+2 | |
| Electronegativity, Pauling | 1.9 | |
| State at RT | Solid, Metal | |
| Melting Point, K | 1356.6 | |
| Boiling Point, K | 2840 |
Appearance and Characteristics
Harmful effects:
Copper is essential in all plants and animals. Excess copper is, however, toxic.
Cooking acidic food in copper pots can cause toxicity. Copper cookware should be lined to prevent ingestion of toxic verdigris (compounds formed when copper corrodes).
Characteristics:
- Copper is a reddish orange, soft metal that takes on a bright metallic luster.
- It is malleable, ductile, and an excellent conductor of heat and electricity – only silver has a higher electrical conductivity than copper.
- Copper surfaces exposed to air gradually tarnish to a dull, brownish color.
- If water and air are present, copper will slowly corrode to form the carbonate verdigris often seen on roofs and statues.
Uses of Copper
- As a result of its excellent electrical conductivity, copper’s most common use is in electrical equipment such as wiring and motors.
- Because it corrodes slowly, copper is used in roofing, guttering, and as rainspouts on buildings.
- It is also used in plumbing and in cookware and cooking utensils.
- Commercially important alloys such as brass and bronze are made with copper and other metals.
- Gun metals and American coins are copper alloys.
- Copper sulfate is used as a fungicide and as an algicide in rivers, lakes and ponds.
- Copper oxide in Fehling’s solution is widely used in tests for the presence of monosaccharides (simple sugars).
