Question

part a
the compound ncl₃ is named nitrogen trichloride, while alcl₃ is simply aluminum chloride. why the difference?
○ the name forms differ because ncl₃ is a molecular compound and alcl₃ is an ionic compound. prefixes such as mono, di, and tri are used for molecular compounds but not for ionic compounds.
○ the name forms differ because ncl₃ is an ionic compound and alcl₃ is a molecular compound. prefixes such as mono, di, and tri are used for ionic compounds but not for molecular compounds.
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Explanation:

To determine the correct option, we analyze the nature of the compounds and naming rules:

1. Compound Types: \( \text{NCl}_3 \) is a molecular (covalent) compound because nitrogen and chlorine are both non - metals and share electrons. \( \text{AlCl}_3 \) is an ionic compound as aluminum (a metal) transfers electrons to chlorine (a non - metal).
2. Naming Rules: For molecular compounds, prefixes (mono, di, tri, etc.) are used to indicate the number of atoms of each element. For ionic compounds, we use the name of the cation (metal or polyatomic positive ion) and the anion (non - metal or polyatomic negative ion) without prefixes (since the ratio of ions is determined by charge balance, and we don't need to indicate the number of each ion with prefixes in the same way as molecular compounds).

• The first option has the compound types reversed (says \( \text{NCl}_3 \) is ionic and \( \text{AlCl}_3 \) is molecular, which is incorrect).
• The second option correctly states that \( \text{NCl}_3 \) is molecular (so we use prefix "tri" for the three Cl atoms) and \( \text{AlCl}_3 \) is ionic (so we just use the names of the ions without prefixes), and also correctly states the naming rule about prefixes being for molecular compounds and not for ionic compounds.

Answer:

The name forms differ because \( \text{NCl}_3 \) is a molecular compound and \( \text{AlCl}_3 \) is an ionic compound. Prefixes such as mono, di, and tri are used for molecular compounds but not for ionic compounds. (The option corresponding to this statement)