Final answer:
An ion is an atom with an electrical charge due to an unequal number of protons and electrons. An atom can become a cation with a positive charge by losing electrons or an anion with a negative charge by gaining electrons.
Step-by-step explanation:
An atom that has an electrical charge due to having a number of electrons unequal to the number of protons is considered an ion. A neutral atom can lose some electrons and become a positively charged particle, called a cation. Conversely, when an atom gains one or more electrons, it exhibits a negative charge and is referred to as an anion. For example, a sodium atom that loses an electron will become a sodium cation with a 1+ charge, while a nitrogen atom that gains three electrons will become a nitride ion with a 3- charge.