Question

Why is calcium dichloride not the correct systematic name for \(\mathrm{CaCl}_{2} ?\)

Short answer

The name "calcium dichloride" is incorrect for \(\mathrm{CaCl}_{2}\) because it implies the presence of two different types of chloride anions, which is not the case. In this compound, there are two chloride ions (Cl⁻), but they are the same type of anion. According to the IUPAC naming system for inorganic compounds, the correct systematic name is "calcium chloride," with the suffix "-ide" to indicate the presence of anions. The prefix system, like "di-", is used for covalent compounds, not ionic compounds like calcium chloride.

Step-by-step solution

Identify the cation and anion

In the compound \(\mathrm{CaCl}_{2}\), we have two elements - calcium (Ca) and chlorine (Cl). Calcium is a metal, and it forms a cation with a +2 charge. Chlorine is a non-metal, and it forms an anion with a -1 charge.

Apply IUPAC rules for naming binary ionic compounds

According to the IUPAC naming system for inorganic compounds, a binary ionic compound is named by stating the name of the cation first, followed by the name of the anion. The name of the anion is derived by taking the root name of the non-metal and adding the suffix "-ide" to it.

Determine the correct systematic name

Following the IUPAC rules, the cation in our compound is "calcium," and the anion is derived from "chlorine" by taking the root name "chlor" and adding the suffix "-ide" to get "chloride." Thus, the correct systematic name for the compound \(\mathrm{CaCl}_{2}\) is "calcium chloride."

Explain why "calcium dichloride" is not correct

The name "calcium dichloride" is incorrect because the use of the prefix "di-" indicates that there are two different types of chloride anions, which is not the case in the given compound. In \(\mathrm{CaCl}_{2}\), there are two chloride ions (Cl⁻), but they are the same type of anion. This prefix system is used in naming covalent compounds, like carbon dioxide (\(\mathrm{CO}_{2}\)), where the "di-" indicates that there are two oxygen atoms bonded to the carbon atom. However, it is not appropriate for ionic compounds like calcium chloride, where the "-ide" suffix is used instead to indicate the presence of anions.