Naming Covalent Compounds Worksheets - Free Printable - Free Printable

Here are the correct names for each covalent compound, following standard IUPAC nomenclature rules for molecular (covalent) compounds:

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1. N₂O₅ → Dinitrogen pentoxide
*Explanation:* Two nitrogen atoms → “di-”, five oxygen atoms → “penta-”, and the second element ends in “-ide”.

2. SeBr₆ → Selenium hexabromide
*Explanation:* One selenium atom (no prefix needed), six bromine atoms → “hexa-”, ending with “-ide”.

3. CH₄ → Methane
*Explanation:* This is a common hydrocarbon. While technically covalent, it’s traditionally named using organic naming: methane (CH₄), ethane (C₂H₆), etc. In strict covalent naming, it would be “Carbon tetrahydride”, but “methane” is universally accepted and expected here.

4. C₆H₆ → Benzene
*Explanation:* This is the common name for this aromatic hydrocarbon. In covalent naming, it could be “Hexacarbon hexahydride”, but that’s not used. “Benzene” is the correct and expected answer.

5. PF₆ → Phosphorus hexafluoride
*Note:* Actually, PF₆⁻ is an ion (hexafluorophosphate), but as written, assuming neutral PF₆ doesn’t exist — the stable compound is PF₅ (phosphorus pentafluoride). However, if we take the formula literally as given, the name would be Phosphorus hexafluoride, even though it’s not a stable neutral molecule. *(Instructor may have meant PF₅ — but we follow what’s written.)*

6. BF₃ → Boron trifluoride
*Explanation:* One boron atom, three fluorine atoms → “tri-” + “fluoride”.

7. P₂I₄ → Diphosphorus tetraiodide
*Explanation:* Two phosphorus → “di-”, four iodine → “tetra-”, ending in “-ide”.

8. S₂Cl₃ → Disulfur trichloride
*Explanation:* Two sulfur atoms → “di-”, three chlorine atoms → “tri-”, ending in “-ide”. *(Note: This compound is unstable and rare, but named conventionally.)*

9. NO₂ → Nitrogen dioxide
*Explanation:* One nitrogen, two oxygen → “di-” + “oxide”. Note: Not “dinitrogen dioxide” — only use prefixes when more than one atom of the first element.

10. P₂O₅ → Diphosphorus pentoxide
*Explanation:* Two phosphorus → “di-”, five oxygen → “penta-”, ending in “-ide”. Also commonly called “phosphorus pentoxide”, but strictly speaking, “diphosphorus pentoxide” is correct for the molecular formula.

11. OF₂ → Oxygen difluoride
*Explanation:* One oxygen, two fluorine → “di-” + “fluoride”. Oxygen is first because it’s less electronegative than fluorine? Wait — actually, fluorine is more electronegative, so by convention, the *less* electronegative element comes first — oxygen is less electronegative than fluorine, so “oxygen difluoride” is correct.

12. CO → Carbon monoxide
*Explanation:* One carbon, one oxygen → “mono-” is used for the second element when there’s only one. So “carbon monoxide” (not “carbon oxide”).

13. BrO₃ → Bromine trioxide
*Explanation:* One bromine, three oxygen → “tri-” + “oxide”. *(Note: This is not the same as the bromate ion BrO₃⁻ — here it’s written as a neutral molecule.)*

14. CBr₄ → Carbon tetrabromide
*Explanation:* One carbon, four bromine → “tetra-” + “bromide”.

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✔ Final Answer Key:

1. Dinitrogen pentoxide
2. Selenium hexabromide
3. Methane
4. Benzene
5. Phosphorus hexafluoride *(Note: Unstable; PF₅ is common)*
6. Boron trifluoride
7. Diphosphorus tetraiodide
8. Disulfur trichloride
9. Nitrogen dioxide
10. Diphosphorus pentoxide
11. Oxygen difluoride
12. Carbon monoxide
13. Bromine trioxide
14. Carbon tetrabromide

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📌 Important Notes:
- For covalent compounds, use Greek prefixes (mono-, di-, tri-, etc.) to indicate number of atoms.
- The first element keeps its elemental name; the second ends in “-ide”.
- “Mono-” is usually omitted for the first element, but is used for the second if there’s only one atom (e.g., CO = carbon monoxide).
- Some compounds like CH₄ and C₆H₆ have traditional names (methane, benzene) that override systematic naming.

Let me know if you’d like the reverse — writing formulas from names!