Elements are the basic constituents of all matter. An element is the simplest form of matter, which cannot split into simpler substances by any chemical or physical method.
In terms of the atomic theory, an element is composed of atoms of the same kind. There are 115 elements known to us at present, out of which 90 are naturally occurring, while 25 have been prepared artificially. A complete list element is given on the inner side of the cover, at the end of the book.
These elements are widely distributed in the earth’s crust in the free as well as in the combined forms. On the basis of chemical and physical properties, the elements are further classified into metals, nonmetals and metalloids.
Only a few elements occur in their pure form. Most elements are present in nature in the combined form, i.e., in the form of their compounds. Common elements cannot be made in very small amounts by using special techniques in laboratories.