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General Science - Chemistry (Metals & Non Metals):

Written By STPORTAL on Sunday, March 18, 2012 | 2:49 PM


General Science - Chemistry (Metals & Non Metals):
 
Metals
Metals have certain characteristic physical properties: they are usually shiny (they have "lustre"), have a high density, are ductile and malleable, usually have a high melting point, are usually hard, and conduct electricity and heat. These properties are mainly because each atom exerts only a loose hold on its outermost electrons (valence electrons); On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Most metals are grayish in color, but bismuth is pinkish, copper is red, and gold is yellow. Some metals display more than one colour, a phenomenon called pleochroism.

Ores
An ore is a mineral containing a metal as a proportion of its content. Usually, it is used in the context of a mineral from which it is economical to extract its metallic component. Ores are mined.
 Substance
 Important Ores
Aluminium
Bauxite Al2O3
Antimony
Stibnite Sb2S3
Beryllium
Beryl , Crysoberyl
Calcium
Lime stone, Marble, Chalk, Gypsum, Alabaster , Flurosper
Chromium
Chromite (Feo Cr2 O3)
Cobalt
Smaltite
Copper
Cuprite (Cu2O), Bornite
Iron
Hematite Fe2O3, Magnatite (Fe3O4)
Lead
Galena (Pbs), Masicot, Serusite
Magnicium
Magnesite, Dolomite, Carnallite
Manganese
Pyrolusite, Hausmannite
Mercury
Cinnabar
Molybdenum
Molybdenite & wulfenite
Nickel
Pantilandite and Gargnierite
Phosphorous
Phosphorite Apatite, Chlorapatite
Potassium
Carnelite , Saltpetre (KNO3)
Silver
Argentite(AgS2)
Sodium
Rock Salt( Nacl) Chile Saltpetre (NaNO3)
Sulphur
Galena, Copper Pyrites & Iron Pyrites
Tin
Cassiterite, Tin stone
Titanium
Rutile (TiO2), Ilmenite
Uranium
Pitchblende (UO2)
Zinc
Zinc Blends, Calamine



There are 3 types of process are employed for the metal extraction. They are Mechanical, Chemical and Electrical.

Some important processes are:

a) Gravity separation: The crushed ore are suspended either in water or an air blast, the heavier metal or metallic mineral particles fall to the bottom of the processing chamber, and the lighter gangue is blown or washed away. Gold and magnetite are separated in this way .

b) Flotation: In this method, finely ground ore is mixed with a liquid. The metal or metallic mineral floats while the gangue sinks

c) Magnetic separation: Metals that have magnetic properties are concentrated by means of electromagnets that attract the metal but do not attract the gangue e.g. magnetite

d) Smelting: the ore is heated with a reducing agent and a flux to a high temperature. The reducing agent combines with the oxygen in a metallic oxide, leaving pure metal; and the flux combines with the gangue to form a slag that is liquid at the smelting temperature and thus can be skimmed off or poured away from the metal. The production of pig iron in blast furnaces is an example of smelting and the process is also used to extract copper, lead, nickel, and many other metals from their ores.

e) Amalgamation is a metallurgical process that utilizes mercury to dissolve silver or gold to form an amalgam. This process has been largely supplanted by the cyanide process, in which gold or silver is dissolved in solutions of sodium or potassium cyanide.

f) Electrolysis: In this process, the metal is deposited at the cathode from aqueous solutions or in an electrolytic furnace. Copper, nickel, zinc, silver, and gold are several examples of metals that are refined by deposition from aqueous solutions. Aluminium, barium, calcium, magnesium, beryllium, potassium, and sodium are metals that are processed in electrolytic furnaces.

Some interesting points
Osmium and iridium (specific gravity 22.6) are the most dense metals, and lithium (specific gravity 0.53) is the least dense. Bismuth has the lowest electrical conductivity of the metallic elements, and silver the highest at ordinary temperatures. Gallium, mercury, cesium, and rubidium are the only metal elements that melt near room temperature

Metalloids
A group of elements called metalloids, intermediate in properties between the metals and the nonmetals, are sometimes considered a separate class.

They have properties intermediate between those of metals and nonmetals. most common is that metalloids are usually semiconductors rather than conductors.

They are boron (B) silicon (Si) germanium (Ge) arsenic (As) antimony (Sb) tellurium (Te) Polonium (Po)


Non metal
A non metal is a substance that conducts heat and electricity poorly, is brittle or waxy or gaseous, and cannot be hammered into sheets or drawn into wire. Non metals gain electrons easily to form anions . About 20% of the known chemical elements are non metals. The oxides of nonmetals are acidic.

The nonmetals are, in order of atomic number:

hydrogen (H) carbon (C) nitrogen (N) oxygen (O) fluorine (F) phosphorus (P) sulfur (S) chlorine (Cl) selenium (Se) bromine (Br) iodine (I) astatine (At)

Alkali metals
Alkali Metals, series of six chemical elements in group 1 (or Ia) of the periodic table They are soft compared to other metals, have low melting points, and are so reactive that they are never found in nature uncombined with other elements. They are powerful reducing agents. The alkali metals are, in order of increasing atomic number, lithium, sodium, potassium, rubidium, cesium, and francium. Francium exists only in a radioactive form.

Alkaline Earth Metals
It is a series of six chemical elements in group 2 (or IIa) of the periodic table. Although rather brittle, the alkaline earth metals are malleable, conduct electricity and when heated, burn readily in air. The alkaline earth metals are, in order of increasing atomic number, beryllium, magnesium, calcium, strontium, barium, and radium. Their oxides are called alkaline earths.

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