International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

During the formation of an ionic compound, how do sodium and chlorine interact?

1. The sodium atom shares its electrons with chlorine

2. The sodium atom donates an electron to chlorine

3. Both atoms retain their electrons

4. Sodium and chlorine do not interact

The correct answer is: The sodium atom donates an electron to chlorine

In the formation of an ionic compound, sodium and chlorine interact through the transfer of electrons. Specifically, the sodium atom donates one electron to the chlorine atom. Sodium has one electron in its outermost shell, which it can easily lose to achieve a stable electron configuration resembling that of the nearest noble gas, neon. When sodium donates this electron, it becomes a positively charged ion (Na⁺). On the other hand, chlorine has seven electrons in its outer shell and requires one more electron to complete its octet, leading to a stable electronic configuration equivalent to that of the noble gas argon. When chlorine accepts the electron from sodium, it becomes a negatively charged ion (Cl⁻). The electrostatic attraction between the positively charged sodium ion and the negatively charged chloride ion results in the formation of the ionic compound sodium chloride (NaCl). This interaction exemplifies how ionic bonds are formed through the transfer of electrons, leading to the stability of both ions involved.