Atoms will combine with each in order to become more chemically stable. Compounds are formed between two atoms that have outer energy levels. The two types of compounds that can be formed between atoms are ionic and covalent. Ionic compounds are formed between two charged atoms. Ionic compounds contain a ion and a ion. Metals will lose electrons to form positive ions and nonmetals will gain electrons to form negative ions. These oppositely charge ions are very attracted to each other and form very strong bonds as a result. Ionic compounds are characterized by crystalline structure, melting and boiling points, and are at room temperature.
Two will combine to form covalent compounds. Covalent compounds are formed when two atoms one or more pairs of electrons. The force of attraction between the nonmetals is relatively weak. Covalent compounds are characterized by melting and boiling points and can be gases, liquids, or soft solids at room temperature.