Lewis structure for calcium hydrogen carbonate Ca(HCO3)2
The Correct Answer and Explanation is :
The Lewis structure for calcium hydrogen carbonate ((\text{Ca(HCO}_3\text{)}_2)) involves both the metal cation (calcium, ( \text{Ca}^{2+} )) and the hydrogen carbonate anion (( \text{HCO}_3^- )).
Step-by-Step Construction of the Lewis Structure:
- Calcium Ion (( \text{Ca}^{2+} )):
Calcium (Ca) has an atomic number of 20 and typically forms a ( \text{Ca}^{2+} ) ion by losing two electrons. In the Lewis structure, this ion will be represented as ( \text{Ca}^{2+} ), which does not have any lone electrons, and its electron shell is completed. - Hydrogen Carbonate Anion (( \text{HCO}_3^- )):
The hydrogen carbonate ion consists of one hydrogen (H) atom, one carbon (C) atom, and three oxygen (O) atoms. The carbon atom forms a central atom, bonded to three oxygen atoms. The oxygen atoms are connected to the carbon through single and double bonds, and one oxygen carries a negative charge.
- In this structure, the hydrogen atom is bonded to one of the oxygen atoms.
- The other two oxygens have single bonds with the carbon and carry lone pairs.
- There is a resonance between the bonding, meaning the double bond could be between the carbon and any of the oxygen atoms.
- Final Lewis Structure:
- The calcium ion (( \text{Ca}^{2+} )) is ionically bonded to two hydrogen carbonate ions (( \text{HCO}_3^- )) since calcium has a ( +2 ) charge and each hydrogen carbonate ion has a ( -1 ) charge.
- The hydrogen carbonate ions each form a stable arrangement with single and double bonds between the carbon and oxygen atoms.
- The overall structure is ionic, with the calcium ion electrostatically attracted to the negatively charged hydrogen carbonate ions.
Explanation:
The Lewis structure for calcium hydrogen carbonate, ( \text{Ca(HCO}_3\text{)}_2 ), highlights the ionic nature of the compound. Calcium donates two electrons, forming ( \text{Ca}^{2+} ), and each hydrogen carbonate ion, ( \text{HCO}_3^- ), balances this by providing a negative charge. The central carbon atom in each ( \text{HCO}_3^- ) ion is bonded to three oxygens, one of which has a single bond with a hydrogen atom. This ion is able to maintain its stability through resonance, allowing the double bond to shift between oxygens. The electrostatic attraction between ( \text{Ca}^{2+} ) and the anions results in a neutral compound.