* Potassium (K) is a metal, and metals tend to lose electrons to form positively charged ions (cations). Potassium has one valence electron and readily loses it to form K⁺.
* Sulfur (S) is a nonmetal, and nonmetals tend to gain electrons to form negatively charged ions (anions). Sulfur has six valence electrons and needs two more to complete its octet. It gains two electrons to form S²⁻.
When potassium and sulfur react, potassium atoms donate their electrons to sulfur atoms, forming an ionic bond. The resulting compound is potassium sulfide (K₂S).
The formula K₂S represents the following:
* Two potassium ions (K⁺) for every one sulfide ion (S²⁻) to balance the charges.
* The overall charge of the compound is neutral.
Key Points:
* Ionic compounds are formed between metals and nonmetals.
* The electrostatic attraction between oppositely charged ions holds the compound together.
* The chemical formula of an ionic compound reflects the ratio of cations and anions needed to achieve neutrality.
