Not all atoms are capable of forming ions. Whether an atom can form an ion depends on its electronic configuration and its position on the periodic table.
Atoms that have less than four valence electrons tend to lose electrons to achieve a stable electron configuration similar to that of a noble gas. These atoms are typically found on the left side of the periodic table and are known as metals. When they lose electrons, they form positively charged ions called cations. Examples include sodium (Na+) and magnesium (Mg2+), which lose one and two electrons, respectively.
On the other hand, atoms that have more than four valence electrons tend to gain electrons to achieve a stable electron configuration. These atoms are usually found on the right side of the periodic table and are known as nonmetals. When they gain electrons, they form negatively charged ions called anions. Examples include chlorine (Cl-) and oxygen (O2-), which gain one and two electrons, respectively.
However, some atoms have a stable electron configuration and do not readily form ions. These atoms are typically found in the noble gas group (Group 18) of the periodic table, such as helium (He), neon (Ne), and argon (Ar). Noble gases have a full valence electron shell and are already in a stable configuration, so they do not readily gain or lose electrons to form ions.
In summary, while most atoms are capable of forming ions, whether an atom can become an ion depends on its electronic configuration and its position on the periodic table. Metals tend to lose electrons to form cations, nonmetals tend to gain electrons to form anions, while noble gases generally do not form ions due to their stable electron configurations.