Copper (Latin Cuprum), Cu, a chemical element of Group I of the Periodic System, atomic number 29, atomic weight 63.546; soft, malleable metal red. Nature copper comprises a mixture of two stable isotopes - 63Su (69.1%) and 65Su (30.9%).
Copper color red, pink in the fracture, in transmission in a thin layer of greenish-blue. The metal has a face-centered cubic lattice parameter a = 3,6074 Å; density of 8.96 g/cm3 (20 ° C).
Atomic radius 1,28 Å; ionic radii Cu + 0,98 Å; Cu2 + 0,80 Å; tpl1083 ° C b.p. 2600 ° C, a specific heat (20 ° C) 385.48 J / (kg · K), T . e 0.092 cal / (g · ° C). The most important and widely used copper properties: high thermal conductivity - at 20 ° C 394.279 W / (mK), that is 0.941 cal / (cm · sec · ° C), low electrical resistivity - at 20 ° C 1.68 · 10-8 ohm-m The thermal expansion coefficient 17.0 x 10-6.
The vapor pressure over copper negligible pressure 133.322 N/m2 (ie, 1 mm Hg) is achieved only at 1628 ° C.
Copper is diamagnetic, nuclear magnetic susceptibility of 5.27 × 10-6. Copper Brinell hardness 350 Mn/m2 (ie 35 kgf/mm2) tensile Mn/m2 220 (ie 22 kgf/mm2) elongation 60%, modulus of elasticity 132,103 Mn / m2 (i.e., 13.2 x 103 kgf/mm2).
By hardening the tensile strength can be increased to 400-450 MN/m2 while elongation decreases to 2%, the electrical conductivity is reduced by 1-3%.
Annealing of the work-hardened copper should be performed at 600-700 ° C. Small amounts of Bi (thousandths of%) and Pb (hundredths of a%) Copper redact do, and admixture of S causes brittleness in the cold.
The chemical properties of copper is intermediate between the elements of the first triad of Group VIII and alkaline elements in group I of the periodic.
Copper, as Fe, Co, Ni, tends to complex, giving colored compounds insoluble sulfides, etc. similarity with alkali metals slightly. For example, copper forms a series of monovalent compounds, but it is more common for the two-valence state. Monovalent copper salts are virtually insoluble in water and easily oxidized to compounds of 2-valent copper salt of 2-valent copper, however, are readily soluble in water and dilute completely dissociated. Hydrated ions Cu2 + are blue. Also known are compounds in which 3-valent copper.
Thus, the action of sodium peroxide on a solution of sodium cuprite Na2CuO2 obtained oxide Su2O3 - red powder begins to give oxygen even at 100 ° C. Su2O3 - a strong oxidizing agent (for example, highlights the chlorine from hydrochloric acid).
Large Copper role in technology due to a number of its properties, and above all a high electrical conductivity, ductility, thermal conductivity. Due to these properties, copper - the main material for the wires and more than 50% of its copper is used in the electrical industry. All impurities reduce the conductivity of copper, but because the metal used in electrical higher grades containing not less than 99,9% Cu.
High thermal conductivity and corrosion resistance of copper can produce important parts of heat exchangers, coolers, vacuum apparatus, etc., about 30-40% of copper are used in a variety of alloys, among which the most important are brass (from 0 to 50% Zn) and high types of bronzes: tin, aluminum, leaded, beryllium, etc. In addition the needs of heavy industry, communications, transportation, some copper (mainly in the form of salts) is used for the preparation of mineral pigments, control pests and plant diseases, as micronutrients , catalysts for oxidation processes, as well as in the leather and fur industry and in the manufacture of artificial silk.
Copper is used as an artistic material from the Copper Age (jewelry, sculpture, utensils, dishes). Forged and cast products made of copper decorated with embossing, engraving and embossing. Ease of processing copper (due to its softness) allows the master to achieve a variety of textures, the thoroughness of detail, subtle modeling of forms. Brassware very nicely golden or reddish tones, as well as to acquire the property shine when grinding. Copper is often gold, Patinir, tinting, decorate with enamel. From the 15th century Copper is also used in the manufacture of printed forms.