The bonding in Na2CO3 could best be described as
A. ionic.
B. covalent.
C. both ionic and covalent.
D. metallic.
The Correct Answer and Explanation is:
Correct Answer: C. both ionic and covalent.
The bonding in sodium carbonate (Na₂CO₃) is best described as both ionic and covalent due to the different types of elements and interactions involved in its structure.
Sodium carbonate is composed of two sodium ions (Na⁺) and one carbonate ion (CO₃²⁻). The interaction between the sodium ions and the carbonate ion is ionic in nature. Sodium, a metal, tends to lose an electron to form Na⁺ cations, while the carbonate ion carries a 2− charge, which is balanced by the two Na⁺ ions. This electrostatic attraction between positively charged sodium ions and the negatively charged carbonate ion forms ionic bonds.
However, within the carbonate ion (CO₃²⁻) itself, the bonding is covalent. The carbonate ion consists of one carbon atom bonded to three oxygen atoms. In this polyatomic ion, the atoms are held together by covalent bonds, where electrons are shared between the atoms. The bonding in CO₃²⁻ also exhibits resonance, where the double bond between carbon and one of the oxygen atoms is delocalized over all three oxygen atoms. This results in all three C–O bonds having the same bond length and strength, which is intermediate between a single and a double bond.
Therefore, Na₂CO₃ contains both types of chemical bonding:
- Ionic bonding between the sodium ions and the carbonate ion.
- Covalent bonding within the carbonate ion itself.
This dual bonding nature is common in salts formed from metal ions and polyatomic ions. Recognizing both types of bonding is crucial for understanding the compound’s properties, such as solubility in water, high melting point, and electrical conductivity when dissolved or molten.
