1. A metal atom: Metals tend to lose electrons and become positively charged ions (cations).

2. A nonmetal atom: Nonmetals tend to gain electrons and become negatively charged ions (anions).

Here are some examples:

* Sodium (Na) and Chlorine (Cl): Sodium (a metal) loses one electron to become Na+, and Chlorine (a nonmetal) gains that electron to become Cl-. These oppositely charged ions attract each other, forming the ionic compound sodium chloride (NaCl), commonly known as table salt.

* Magnesium (Mg) and Oxygen (O): Magnesium (a metal) loses two electrons to become Mg2+, and Oxygen (a nonmetal) gains two electrons to become O2-. This results in the formation of magnesium oxide (MgO).

Remember: The key is that one atom needs to have a strong tendency to lose electrons, while the other needs a strong tendency to gain electrons.