Metal – All About Metals
The metals are solids at ordinary temperature, except mercury, which is lichid. His property characteristic of metals, such as electrical conductivity and thermal conductivity, they are explained by structural and electronic metals. In crystals atoms settlement is done on the principle of a structure more compact. Therefore metals crystallize in one of three types of crystalline networks: compact cubic, hexagonal and cubic compact internal centered. In compact metals, the atoms are bound together by valence electrons which did not belong to each atom in hand, but all neighboring atoms, the energy bands are assigned.
Metals shows different properties from those of non-metals. All the characteristic properties of metals are available in solid and liquid metals. Gaseous metals no longer distinguishable from non-metals. Metals have a characteristic luster, called metallic luster due to light reflection of their power. Metals are opaque even in thin layers because light waves hitting the mobile electrons in the metal are amortized and are not shared.
Color metals is varied. Most metals in compact state are white, meaning white, white metal; thus, lead, silver white metals are considered. But few are colored metals: copper is reddish-yellow, yellow gold, yellow cesium etc. When the fine powder, almost all metals have gray-black color. In the technique, metals are classified in: black or ferrous metals, which means iron with cast irons and steels, and ferrous metals, ferrous meaning. Metal density varies widely; for example, lithium or potassium has the density of 0.53 density is 0.86, while platinum has a density of 21.45 and osmium, the heaviest metal has density of 22.5.
It is common to consider metals with a density less than 5 light metal, and the density over 5 heavy metals. Thus, potassium, sodium, calcium, magnesium, aluminum metal are regarded as light, while zinc, tin, iron, heavy metals are copper. The melting point than strengths vary from metal to metal. Mercury, the only liquid metal has a melting point of -39 ° C; potassium and sodium melt at temperatures below 100 ° C (potassium to 63.5 ° C, rather than 1000 ° C, for example, copper melts at 1083 ° C, sodium iron to 97.8 ° C). There are, however, metals whose melting point is 1536 ° C higher, tungsten at 3410 ° C. In general, the metals with low atomic volume melt at high temperatures, while metals with high atomic volume melt at low temperatures because it destroys their crystal network easier. The difference between the melting points of metals is used for metal separation between them in the manufacture of alloys and metal.
Specific electric conductivity, ie the conductivity of metals is high. When not under the influence of an external electric field, the metal does not manifest a compact transport specifications, noticeably; occupied molecular orbital electrons of the band moves without privileged direction. As a result, the electrons occupy orbitals not participate in power transmission. Applying a potential difference, occupied molecular orbital electrons from gaining extra energy molecular orbitals are promoted neighbors, adrift in energy band partially occupied and taken over power transport. It is understood that the alkali metals, which is filled valence band half have better conductivity than alkaline earth metals, in which the valence band is completely occupied.