Elements and Compounds
An element is a pure substance which cannot be split into two or more simpler substances by any physical or chemical methods. Today, we know about the existence of 118 elements, out of which 90 are found in nature while remaining are man-made. Inside of element, you will find identical atoms. An atom is the smallest unit of an element. The four main categories of elements are metals, non-metals, metalloids and noble gases.
Compound is a pure substance formed by the chemical combination of two or more elements in a fixed ratio by mass. A molecule is the smallest unit of a compound which has independent existence. On the other hand, mixture has no fixed composition, i.e. it is formed by mixing two or more substances in any ratio without any chemical reaction. For example, sugar solution can be formed by mixing varying proportions of sugar and water.