ABSTRACT
In 4.3 atoms are described as electrically neutral entities. Under some circumstances, however, they can gain or lose electrons, and thus become electrically charged. This process is called ionization and it gives rise to entities known as ions. Some of the very common elements in the environment exist principally in ionic form. When one or more electrons are lost from an electrically neutral atom, the number of protons in the atomic nucleus exceeds the number of electrons. The result is a positively charged entity, called a cation. Conversely, when one or more electrons is acquired by an electrically neutral atom, the number of protons in the nucleus is less than the number of electrons. The result is a negatively charged entity, called an anion.
