domingo, 6 de marzo de 2011


There are about 118 elements, 107 of which are naturally occurring. Metals and non-metals are characterized by distinctly different physical and chemical properties. At present about 80 metals are known to us. Metals can be shaped like clay, are heat-resistant, and are not fragile.

Though the non-metals are only 22 in number, they are the major constituents of earth, air and oceans. At room temperature, over half of the non-metals are gases, except bromine, which is a liquid. The most abundant non-metal in the earth's crust is oxygen, which constitutes about 50% of the earth's crust and along with nitrogen it forms the main constituents of air. The next abundant non metal is silicon which constitutes about 26% of the earths crust. Oxygen and silicon are the two major constituents of earth. Hydrogen and oxygen are the two major constituents of the oceans.

Position of Metals and Non-metals in the Periodic Table

One can easily differentiate between metals and non-metals based on their placement on the Periodic Table of the Elements. Metals occupy the groups on the left of the periodic table. Group IA consists of highly reactive metals called the alkali metals, while group 22 elements are called alkaline earth metals. Elements between group IIA and IIIA are all called transition metals. The Various Kinds of Metals are as shown below: The non-metals are elements (with the exception of hydrogen) that are found to the right on the Periodic Table i.e., groups IIIA, IVA and VA. The non-metallic character of these elements increases from top to the bottom of the group. For example, in group VA the first and second members are non-metals, the third and fourth are metalloids and the last member is a metal. The metalloids are a group of elements which have properties similar to both the metals and non-metals. These metalloids are: Boron, silicon, germanium, arsenic, antimony, tellurium and astatine. The non-metals are elements found to the right of these metalloids, including the element, hydrogen.

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