A negative ion is the particle such as a neutral atom or molecule gets one or more electrons. In chemical reactions, the metal atom loses the outermost electrons which with positive charge. And the non – metallic atoms get electrons, so that the atoms or groups of atoms that take part in the reactions take charge. A charged atom is called an negative ion. A positively charged atom is called a positive ion. In the air, the positive ion is harm to our body. Only the negative ion is good for our healthy.