Question

compound type: ionic or covalent? compound formula compound name ionic na⁺ br⁻→nabr sodium bromide covalent n₂s dinitrogen monosulfide ionic cao calcium oxide covalent so₃ sulfur trioxide ionic li⁺ s⁻²→li₂s lithium sulfide covalent alcl₃ aluminium trichloride ionic mgbr₂ magnesium dibromide covalent n⁺⁵ o⁻²→n₂o₅ dinitrogen trioxide (with subscripts 2 and 5)

Explanation:

Step1: Analyze Compound Type Rules

Ionic compounds form between metals (or polyatomic cations) and non - metals (or polyatomic anions). Covalent compounds form between non - metals.
- For \( \text{NaBr} \): Na is a metal, Br is a non - metal. So it's ionic. The formula should be \( \text{NaBr} \) (the student's \( \text{Na}^{+}\text{Br}^{-}\to\text{NaBr} \) is correct in concept, just the notation for sodium ion is \( \text{Na}^+ \) not \( \text{Na}^{++} \)).
- For \( \text{N}_2\text{S} \): N and S are non - metals. So it's covalent. The name should be dinitrogen sulfide (the student's "dinitrogen monosulfide" has an incorrect prefix as there is no "mono" needed here as the subscript of S is 1 and for the first element in a covalent compound, if the subscript is 1, we don't use a prefix. Wait, actually, for \( \text{N}_2\text{S} \), the correct name is dinitrogen sulfide.
- For \( \text{CaO} \): Ca is a metal, O is a non - metal. So it's ionic. The name is calcium oxide (correct as the student wrote).
- For \( \text{SO}_3 \): S and O are non - metals. So it's covalent. The name is sulfur trioxide (correct as the student wrote).
- For \( \text{Li}_2\text{S} \) (the student has \( \text{Li}^+ \text{S}^{2 - }\to\text{Li}_2\text{S} \), note the correct formula from ions \( \text{Li}^+ \) and \( \text{S}^{2 - } \) is \( \text{Li}_2\text{S} \), the student wrote "Li₂S" as "Li₂S" (with a typo "Li₂S" written as "Li₂S" maybe? And the name is lithium sulfide (correct as the student wrote)).
- For \( \text{AlCl}_3 \): Al is a metal, Cl is a non - metal? Wait, no. Al is a metal, but \( \text{AlCl}_3 \) has some covalent character, but generally, for the purpose of this basic classification, Al is a metal and Cl is a non - metal, but actually, \( \text{AlCl}_3 \) is a covalent compound in the solid state (dimer \( \text{Al}_2\text{Cl}_6 \)) and ionic in solution? But at the basic level, when classifying, since Al is a metal and Cl is a non - metal, but the student classified it as covalent. Wait, no, \( \text{AlCl}_3 \) is a covalent compound. Because the electronegativity difference between Al and Cl is not large enough to form a typical ionic bond. Al is a metalloid - like in bonding with non - metals here. So the student's classification as covalent is correct. The name: Al and Cl are non - metals (in terms of covalent bonding here), the name is aluminum trichloride or aluminium trichloride (the student wrote "Aluminium trichloride" which is correct in British English, "Aluminum trichloride" in American English).
- For \( \text{MgBr}_2 \): Mg is a metal, Br is a non - metal. So it's ionic. The formula is \( \text{MgBr}_2 \) (correct), and the name should be magnesium bromide (the student wrote "Magnesium dibromide" which is incorrect. In ionic compounds, we don't use prefixes. So the correct name is magnesium bromide.
- For \( \text{N}_2\text{O}_3 \): N and O are non - metals. So it's covalent. The name is dinitrogen trioxide (correct as the student wrote, and the formula from ions \( \text{N}^{3+} \) and \( \text{O}^{2 - } \)? Wait, no, \( \text{N}_2\text{O}_3 \) is a covalent compound, formed by sharing electrons. The student's ion notation for forming \( \text{N}_2\text{O}_3 \) is incorrect. Covalent compounds are not formed by the transfer of electrons (ionic bond) but by sharing (covalent bond). So the student's mistake here is using ionic bond formation for a covalent compound.

Step2: Correct the Errors

- \( \text{NaBr} \): Ionic, formula \( \text{NaBr} \) (sodium ion is \( \text{Na}^+ \), not \( \text{Na}^{++} \)).
- \( \text{N}_2\text{S} \): Covalent, name dinitrogen sulfide (not "dinitrogen monosulfide").
- \( \text{Li}_2\text{S} \): Ionic, formula \( \text{Li}_2\text{S} \) (from \( \text{Li}^+ \) and \( \text{S}^{2 - } \), the student's formula derivation is correct in concept but the sodium ion notation was wrong earlier, and for \( \text{Li}_2\text{S} \), the name is lithium sulfide (correct).
- \( \text{AlCl}_3 \): Covalent (correct classification), name aluminum trichloride (or aluminium trichloride), and it's formed by covalent bonding, not ionic.
- \( \text{MgBr}_2 \): Ionic, name magnesium bromide (not "Magnesium dibromide").
- \( \text{N}_2\text{O}_3 \): Covalent, formed by covalent bonding (not ionic bond formation as the student showed with ions), name dinitrogen trioxide (correct name).

Answer:

The main errors are:

1. Sodium ion notation in \( \text{NaBr} \) formation: should be \( \text{Na}^+ \) not \( \text{Na}^{++} \).
2. Name of \( \text{N}_2\text{S} \): should be dinitrogen sulfide (not "dinitrogen monosulfide").
3. Name of \( \text{MgBr}_2 \): should be magnesium bromide (not "Magnesium dibromide").
4. Bond - type misunderstanding for \( \text{N}_2\text{O}_3 \): it's covalent, formed by sharing electrons, not ionic bond formation from ions.
5. For \( \text{AlCl}_3 \), while the classification as covalent is correct, the student should know it's formed by covalent bonding (not ionic).