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10. METAL TYPE OF THE CHEMICAL BOND.
Metals and their alloys crystallize in the form of metal lattices. Nodes are engaged in metal lattice with positive ions of metals. The valence electrons which have separated from atoms of metals and remained in nodes of crystal lattice ions more or less freely move in space between cations and cause electric conductivity of metals. Between ions and free electrons there are electrostatic interactions which are origin of metallic bond.
SCHEME OF FORMATION OF THE METALLIC BOND.
The metallic bond has similarity as with ionic (it is formed due to interaction between charged particles: electrons and ions), and with covalent (there is nationalization of electrons, but in difference from covalent linkage where electrons are localized about certain atoms, electrons in metals are socialized for all crystal). Free electrons are called sometimes electron gas.
Cations in metal lattices do not possess progress, and make fluctuations around the provision of lattice sites. Amplitude of these fluctuations increases at temperature increase, and at achievement of temperature of melting of metal the lattice collapses. Temperature of melting of metals, as a rule increases with increase in number of valence electrons in their atoms
ALLOYS.
Mixes of two or more individual metals are called alloys. In alloys there can be at small amounts also some nonmetals (carbon, sulfur, silicon). Widespread method of receiving alloys is joint heating of their components to full fusion of mix. However some metals are not alloyed with each other in any relations.
Metal alloys can be classified so: interstitial solid solutions (part of mezhuzelny cavities of lattice is engaged with atoms of other element, for example carbon atoms in iron-cast iron and steel); solid solutions of substitution (part of atoms of the main substance is replaced with atoms of impurity element - tin solder-64 of part of tin and 36 leads); mixes of individual crystals of metals; mixes of crystals of intermetallic compounds (the alloyed metals form chemical connections - at bronze there is Cu3Sn connection)