In periodic Mendeleev's system of metals from all chemical elements absolute majority. They are divided into several groups in the table and also are classified by a number of signs.
Main classification of metals
Ninety six places from hundred eighteen elements of the periodic table of Mendeleyev are taken by metals. They are divided into several groups: six elements in group of alkaline metals, six in group alkaline-earth, thirty eight - in the most numerous group of transitional metals, eleven in group of lungs, seven in group of semi-metals, fourteen in group lanthanides plus lanthanum, fourteen in the group which is not studied up to the end actinoids plus actinium.
There are two metals which do not adjoin one of the famous groups. It is magnesium and beryllium. Metals and their alloys are divided into two main classes: ferrous and non-ferrous metals. The first includes iron and all solid mixes on its basis. In the second - all other metals and their alloys. Sometimes rank chrome as ferrous metals.
Iron — one of the most widespread metals, ranks second after aluminum on the content in earth crust. Perhaps, it is one of the most known elements in the history of mankind which laid the foundation for the heavy industry.
Metals are also classified by density on ultralight, easy, heavy and superheavy. Metals from subgroup heavy as iron, copper, zinc, molybdenum, participate in biological processes of the person and are called minerals, making three percent of all weight of a human body. Also metals can be classified as refractory. They has high temperature of melting and resistance to wear. Such rare metals as niobium and tantalum and also known for all on incandescence thread tungsten belong to this class. Metals usually contain in composition of ores or are sprayed between other elements as, for example, rubidium.
There is a special class of metals - noble, or precious, metals. It all known gold and silver and also platinum and five metals of platinum group. They have property not to be exposed to corrosion and oxidation and also these are very rare elements in the nature. Only because medieval scientists wanted to transform lead to gold, there was such science as chemistry.
Alchemists made an invaluable contribution to development of science, discovered a number of metals and investigated their properties. They considered soul of all metals mercury.
Precious metals are minimum subject to changes in time, they blow the beauty the human mind, become usual for the person as a jewelry and have the high price.