Copper is the first metal widely used by mankind.
About 3000 BC, mankind began to use copper
Later, bronze (copper-tin alloy) with higher strength and easier processing appeared, and became an important material for manufacturing production tools and weapons before the appearance of ironware
The use of bronze promoted the development of agricultural production.
Historically, the period from 3000 BC to 1000 BC where bronze occupies an important position is called the "Bronze Age" (also known as the "Bronze Age")
Among all metals, copper subgroup elements have the best electrical and thermal conductivity (of which silver is the first); they also have good ductility
Copper subgroup elements are easy to form alloys, especially copper alloys, such as brass (containing 40% zinc), bronze (containing about 15% tin, 5% zinc), cupronickel (containing 13%-15% nickel) and so on
The metallicity of copper subgroup elements decreases with the increase of atomic number, which is exactly the opposite of alkali metals
Copper is relatively stable in dry air, but in contact with humid air containing carbon dioxide , a layer of patina will slowly form on the surface of copper.
2Cu+O 2 +H 2 O+CO 2 =Cu(OH) 2 ·CuCO 3
Silver and gold do not react in the air
If the air contains H 2 S gas, a black film of Ag 2 S will be formed on the surface quickly after contact with silver, which will make the silver lose its silver-white luster
Copper, silver, and gold cannot react with dilute hydrochloric acid or dilute sulfuric acid
Copper and silver are soluble in nitric acid and react slowly with hot concentrated sulfuric acid
Among the copper sub-group elements, gold has the worst activity and is insoluble in nitric acid but only soluble in aqua regia
Au+4HCl+HNO 3 =HAuCl 4 +NO+2H 2 O
The red hot copper reacts with oxygen in the air to produce CuO, which decomposes to Cu 2 O at high temperatures
Silver and gold are also stable in the air at high temperatures
Copper strong ligand (e.
, the CN - ) when the action of water can be discharged with H 2
8CN + 2Cu - + 2H 2 O = 2 [a Cu (the CN) .
4 ] .
3 - + 2OH - + H 2
In the presence of oxygen, Cu can also react with ligands with weaker coordination capabilities
+ 8NH 2Cu .
3 + O 2 + 2H 2 O = 2 [a Cu (NH2 .
3 ) .
4 ] 2 + + 4OH -