Final answer:
An atom with a differing number of electrons than protons is described as an 'ion'. A 'cation' forms when a neutral atom loses electrons and gains a positive charge, while an 'anion' forms by gaining electrons and acquiring a negative charge.
Step-by-step explanation:
An atom with a number of electrons that is higher (anion) or lower (cation) than what's indicated on the periodic table is described using the term ion from atomic structure. When a neutral atom loses one or more electrons, it becomes a cation, which means it has a positive charge. Conversely, when a neutral atom gains one or more electrons, it becomes an anion, which means it has a negative charge.
For example, when sodium (Na) loses an electron, it becomes a sodium cation (Na+), and when chlorine (Cl) gains an electron, it becomes a chloride anion (Cl-). This process results in ions, which are crucial for the formation of ionic bonds, where the oppositely charged ions attract each other to form stable compounds.
The additional information about ions gaining or losing electrons to achieve a full valence shell confirms their importance in chemical bonding and stability, often obeying the octet rule. This rule implies that atoms tend to gain or lose electrons to have eight electrons in their valence shell, which is the most stable electron configuration for many elements.