What is the defining characteristic of an ionic compound?

The defining characteristic of an ionic compound is that it is formed between elements with a significant difference in electronegativity, typically 2 or more. This substantial difference indicates a strong ability of one atom to attract electrons away from another, leading to the formation of ions. In ionic compounds, one element (usually a metal) donates electrons to another element (usually a non-metal), resulting in the creation of positively charged cations and negatively charged anions. These oppositely charged ions then attract each other, resulting in an ionic bond.

For example, when sodium (Na), which has a low electronegativity, reacts with chlorine (Cl), which has a high electronegativity, sodium donates an electron to chlorine. This transfer creates Na⁺ and Cl⁻ ions, which come together to form sodium chloride (table salt), an ionic compound. The strong electrostatic forces between the oppositely charged ions contribute to the stability and properties typical of ionic compounds, such as high melting and boiling points.

In contrast, the other options describe conditions that do not accurately represent the characteristics of ionic compounds. Electronegativity differences of less than 1 generally indicate covalent bonding, while an electronegativity difference of