CHEMISTRY      Element     An element is a pure chemical substance that has atoms with the same number of protons throughout. There are 117 known elements out of which about 95 occur naturally on earth. The rest 22 are artificially prepared elements. It is clear from the table that elements can be divided into four broad parts namely metals, non-metals, metalloids and noble gases.     METALS There are about 84 known metals which are further divided into Alkali metals, Alkaline earth metals, Lanthanides, Actinides, Transition Elements and other metals. Their major physical properties are superior electric and thermal conductivity, high luster, density, and malleability; they form basic oxides and have higher melting and boiling points.     NON-METALS There are about 18 non-metals or non metallic elements including noble gases. Their properties are not strictly defined but they tend to show characteristics like poor conductivity of heat and electricity, low density, dull luster, brittle, they form acidic oxides they have higher electro negativity and lower melting and boiling points.     METALLIODS Metalloids are those elements which show properties of both metals and non metals. There are about 8 elements in this category. They are known to form Amphoteric Oxides i.e. they can either react as acid or base. Also, they are often used in semiconductors which make them useful in electrical components.     NOBLE GASES There are about 7 noble gases and are known to react rarely. They are monatomic gases which are usually odorless, colorless, tasteless, and nonflammable under normal conditions and their boiling and freezing points are lower than that of any other substance known.     Standard periodic table