Final answer:
An atom becomes an ion by losing or gaining electrons, resulting in a positive charge for a cation or a negative charge for an anion. The charge depends on the balance between the number of protons and electrons in the ion.
Step-by-step explanation:
If an atom loses or gains an electron, it becomes an ion. An ion is an atom that has a different number of protons and electrons, which gives it a positive or negative charge. When an atom loses one or more electrons, it becomes a positively charged ion, known as a cation. Conversely, if an atom gains electrons, it becomes a anion with a negative charge. For example, a neutral sodium atom becomes a sodium cation (Na+) when it loses one electron, and a neutral fluorine atom becomes a fluoride anion (F−) when it gains one electron.
The process of changing into a cation or an anion depends on whether the atom loses or gains electrons, which is related to the atom's electron configuration. The last electron(s) in the outermost orbital are typically involved in this process. For main group elements, the last orbital gains or loses the electron, while for transition metals, the last s orbital loses an electron before the d orbitals.