Earth is an abundant source of materials. The air we breathe, the water we drink, stones and rocks, almost everything that is around us, are all useful to man for some purpose or the other. Gaseous materials like Oxygen, Nitrogen and Carbon dioxide are found in the atmosphere. Common salt and various other salts of sodium, magnesium and calcium are found dissolved in water bodies, like the oceans, rivers and lakes.
The progress of the civilization was first benchmarked by man's increasing knowledge and usage of metallic deposits in the earth's crust. Early man used stones, bones and wood to fulfill their requirements of hunting, cooking and building. The first metals to be found and used were copper, silver and gold as they could be easily extracted. By 2000 B.C. he acquired the knowledge of extracting iron from its ores by heating and this period came to be known as "Iron Age". Bronze was widely used for many years and this epoch of prehistory became "Bronze Age". As time went by, minerals were found to produce metals with different properties. These developments indicate a gradual change in the life style of mankind. Today metals are so vital to the modern man that it is unthinkable to live without them. They are essential for the construction of houses, transportation, communication, electricity, household articles, scientific instruments, coins etc. More than 75% of the known elements are metals.There are about 103 elements, 92 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 II A 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:
| Group VA | Nitrogen, phosphorous, Non-metals | Arsenic, Antimony ,Metalloids | Bismuth Metal |
