Answer the following questions regarding Na2CO3. Hint: you need to draw the Lewis structure for Na2CO3. Na2CO3 is a(n) — A. ionic compound B. molecular compound. Na2CO3 has – A. covalent bonds only B. ionic bonds only C. both covalent and ionic bonds. Na2CO3 — (follows OR does not follow) the octet rule. Na2CO3 — (exhibits OR does not exhibit) resonance.
The correct answer and explanation is:
Correct Answers:
- Na₂CO₃ is a(n): A. Ionic compound
- Na₂CO₃ has: C. both covalent and ionic bonds
- Na₂CO₃: follows the octet rule
- Na₂CO₃: exhibits resonance
Explanation (Approximately 300 words):
Sodium carbonate (Na₂CO₃) is an ionic compound, as it is composed of metal (Na⁺) and polyatomic ion (CO₃²⁻). Sodium (Na) is a Group 1 alkali metal that readily loses one electron to form a Na⁺ cation. Since there are two sodium atoms, they each donate one electron, providing a total of two positive charges to balance the -2 charge of the carbonate ion (CO₃²⁻).
The carbonate ion (CO₃²⁻) itself is a polyatomic ion with covalent bonding among its carbon and oxygen atoms. The Lewis structure of CO₃²⁻ reveals that carbon forms three bonds with the surrounding oxygen atoms: one double bond and two single bonds. However, due to resonance, the position of the double bond shifts among the three oxygen atoms. This means the actual structure of CO₃²⁻ is a resonance hybrid, where all three C–O bonds are equivalent and have a bond order of about 1.33.
Thus, Na₂CO₃ contains both ionic bonds (between Na⁺ and CO₃²⁻) and covalent bonds (within the carbonate ion).
Regarding the octet rule, each atom in CO₃²⁻ satisfies the octet rule: carbon has four bonds (8 electrons), and each oxygen has either two bonds and two lone pairs or one bond and three lone pairs, giving each atom a full octet.
Finally, resonance occurs in Na₂CO₃ due to the structure of the carbonate ion. As mentioned, the location of the double bond among the oxygen atoms is not fixed, which is a classic sign of resonance. Therefore, Na₂CO₃ exhibits resonance, contributing to the stability of the carbonate ion.