The word ‘atom’ was coined from the Greek word ‘atomos’ meaning of ‘a’ in the word is ‘not’ and ‘tomos’ means ‘cut’. Together it became impossible to cut. Investigations on atoms have been started over a long period of time and still, it is continuing. The basic definition of atoms is “Atoms are small indivisible particles and every matter that we see are made up of atoms”
Positive ions or cations are formed when an atom loses an electron. This concept can be cleared with the help of an example. A sodium atom consists of 11 protons and 11 electrons. It is electrically neutral when it loses an electron it becomes Na+ ion. The charge of this ion is +1
Negative ions or anions are formed when an atom gains an electron. For example, a chlorine atom consists of 17 electrons and 17 protons. When it gains an electron, it becomes Cl− ion. The charge of this ion is −1.