What is an ionic compound formed between?

An ionic compound is formed between metals and non-metals due to the nature of their electron configurations and bonding tendencies. Metals tend to lose electrons, becoming positively charged cations, while non-metals usually gain electrons to achieve a full valence shell, resulting in negatively charged anions.

When a metal reacts with a non-metal, the metal donates electrons to the non-metal. This electron transfer leads to the formation of electrostatic attractions between the oppositely charged ions, resulting in the formation of an ionic compound. Examples include sodium chloride (NaCl) where sodium (a metal) transfers an electron to chlorine (a non-metal), creating Na⁺ and Cl⁻ ions.

The other choices involve combinations that do not typically lead to ionic bonding. Two non-metals generally form covalent bonds by sharing electrons rather than transferring them. Non-metals and noble gases do not react under standard conditions because noble gases are already stable with full valence shells. Similarly, two metals do not form ionic compounds since there would be no electron transfer; they would more likely form metallic bonds characterized by a sea of delocalized electrons. Thus, the formation of ionic compounds is specifically a result of the interaction between metals and non-metals.