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Naming Covalent Compounds & Acids Worksheet with Answers (Grade 11)

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📄 Naming Covalent Compounds & Acids Worksheet with Answers (Grade 11)

Practise naming molecular compounds and acids with this free Grade 11 chemistry worksheet.

This free naming covalent compounds worksheet gives Grade 11 students 37 questions on naming molecular compounds and acids, from carbon dioxide to sulfurous acid.

Students practise Greek prefixes in both directions, learn the common names every chemist uses, name binary acids and oxyacids, and decide when to use ionic or molecular naming. A complete answer key is included.

  • Grade 11 · SCH3U
  • 37 marks
  • 30–40 minutes
  • Answer key included

What's in This Naming Covalent Compounds Worksheet

The sheet covers both halves of the nomenclature lesson that usually follows ionic naming: molecular compounds and acids.

PartSkill practisedMarks
AMolecular compounds: formula → name6
BMolecular compounds: name → formula6
CCommon names (water, ammonia, methane, hydrogen peroxide)4
DBinary acids4
EOxyacids, both directions8
FIonic or molecular? Choose the naming system4
GSpot the mistake3
HChallenge: per- and hypo- acids2

It matches the Ontario SCH3U expectations for naming compounds in the Matter, Chemical Trends and Chemical Bonding unit.

How to Name Covalent (Molecular) Compounds

Covalent compounds are made of two non-metals, so there are no charges to set the ratio. Instead, the name tells you how many atoms there are using Greek prefixes:

12345678910
monoditritetrapentahexaheptaoctanonadeca
  1. Name the first element and add a prefix only if there is more than one atom. Never use "mono" here.
  2. Name the second element with a prefix and an -ide ending: dioxide, trichloride, hexafluoride.
  3. Drop the final a or o before "oxide" so it reads smoothly: monoxide, pentoxide.

So N2O5 is dinitrogen pentoxide and PCl5 is phosphorus pentachloride. If students are still unsure whether a compound is ionic or covalent, start with our ionic or covalent worksheet. The naming ionic compounds worksheet covers the other naming system, and this naming covalent compounds worksheet builds on both.

How to Name Acids

Acids are compounds that release H+ ions in water, which is why their formulas carry (aq). There are two patterns:

  • Binary acids (hydrogen + one non-metal): hydro + root + -ic acid. HCl(aq) is hydrochloric acid; H2S(aq) is hydrosulfuric acid.
  • Oxyacids (contain a polyatomic ion with oxygen): an -ate ion becomes an -ic acid, and an -ite ion becomes an -ous acid. Nitrate gives nitric acid; nitrite gives nitrous acid.

Some textbooks also accept IUPAC names such as "aqueous hydrogen sulfate" for H2SO4(aq), but the classical names on this sheet are the ones students will see most often. For more detail, see the IUPAC nomenclature page and the Wikipedia article on oxyacids.

Naming Covalent Compounds Practice Questions

These are the same questions as in the naming covalent compounds worksheet PDF. Try them, then open the answer key below.

Part A – Molecular Compounds: Formula → Name

  1. CO
  2. CO2
  3. N2O
  4. PCl5
  5. SF6
  6. CCl4

Part B – Molecular Compounds: Name → Formula

  1. nitrogen trifluoride
  2. dinitrogen pentoxide
  3. sulfur trioxide
  4. carbon disulfide
  5. diphosphorus trioxide
  6. silicon tetrachloride

Part C – Common Names

  1. H2O
  2. NH3
  3. CH4
  4. H2O2

Part D – Binary Acids

  1. HCl(aq)
  2. HBr(aq)
  3. HF(aq)
  4. H2S(aq)

Part E – Oxyacids

Formula → name

  1. HNO3(aq)
  2. HNO2(aq)
  3. H2SO4(aq)
  4. H2CO3(aq)
  5. H3PO4(aq)

Name → formula

  1. sulfurous acid
  2. chloric acid
  3. chlorous acid

Part F – Ionic or Molecular? Name It

Decide which naming system applies, then write the name.

  1. CaCl2
  2. PCl3
  3. FeO
  4. SO2

Part G – Spot the Mistake

  1. A student names CO as “monocarbon monoxide.”
  2. A student names NaCl as “sodium monochloride.”
  3. A student names HNO3(aq) as “hydronitric acid.”

Part H – Challenge

  1. Perchlorate is ClO4−. Name the acid HClO4(aq).
  2. Hypochlorite is ClO−. Name the acid HClO(aq).

Naming Covalent Compounds Worksheet Answer Key

Open each part to check your work. The printable answer key is on pages 3–4 of the PDF.

Part A answers (Q1–6)
  1. CO → carbon monoxide
  2. CO2 → carbon dioxide
  3. N2O → dinitrogen monoxide
  4. PCl5 → phosphorus pentachloride
  5. SF6 → sulfur hexafluoride
  6. CCl4 → carbon tetrachloride
Part B answers (Q7–12)
  1. nitrogen trifluoride → NF3
  2. dinitrogen pentoxide → N2O5
  3. sulfur trioxide → SO3
  4. carbon disulfide → CS2
  5. diphosphorus trioxide → P2O3
  6. silicon tetrachloride → SiCl4
Part C answers (Q13–16)
  1. H2O → water
  2. NH3 → ammonia
  3. CH4 → methane
  4. H2O2 → hydrogen peroxide
Part D answers (Q17–20)
  1. HCl(aq) → hydrochloric acid
  2. HBr(aq) → hydrobromic acid
  3. HF(aq) → hydrofluoric acid
  4. H2S(aq) → hydrosulfuric acid
Part E answers (Q21–28)
  1. HNO3(aq) → nitric acid
  2. HNO2(aq) → nitrous acid
  3. H2SO4(aq) → sulfuric acid
  4. H2CO3(aq) → carbonic acid
  5. H3PO4(aq) → phosphoric acid
  1. sulfurous acid → H2SO3(aq)
  2. chloric acid → HClO3(aq)
  3. chlorous acid → HClO2(aq)
Part F answers (Q29–32)
  1. CaCl2 → Ionic: calcium chloride
  2. PCl3 → Molecular: phosphorus trichloride
  3. FeO → Ionic: iron(II) oxide
  4. SO2 → Molecular: sulfur dioxide
Part G answers (Q33–35)
  1. “Mono” is never used on the first element. Correct: carbon monoxide
  2. NaCl is ionic, and prefixes are only for molecular compounds. Correct: sodium chloride
  3. “Hydro-” is only for binary acids. Nitrate (-ate) becomes -ic. Correct: nitric acid
Part H answers (Q36–37)
  1. perchloric acid
  2. hypochlorous acid

5 Common Naming Mistakes

Parts F and G of the naming covalent compounds worksheet target these directly.

  1. Using prefixes on ionic compounds. "Sodium monochloride" is wrong because ionic names never use prefixes.
  2. Putting mono on the first element. CO is carbon monoxide, not monocarbon monoxide.
  3. Keeping the vowel before oxide. Write pentoxide, not pentaoxide, and monoxide, not monooxide.
  4. Adding hydro- to oxyacids. Hydro- is only for binary acids. HNO3(aq) is nitric acid.
  5. Swapping -ic and -ous. -ate ions become -ic acids; -ite ions become -ous acids. A memory trick: "I ate something icky."

How to Use This Naming Covalent Compounds Worksheet in Class

As a teacher, I use it right after ionic naming:

  • Lesson practice: Parts A–C after introducing prefixes.
  • Acids lesson: Parts D and E once binary acids and oxyacids are taught.
  • Mixed review: Parts F–H as a test warm-up, since students most often lose marks by using the wrong naming system.

Then check understanding with the acids and bases quiz or the chemical bonding quiz.

Frequently Asked Questions

Is this naming covalent compounds worksheet free?

Yes. The worksheet and answer key are free to download and print as a PDF, with no account needed.

How do you name a covalent compound?

Use Greek prefixes to show how many atoms of each element there are, name the second element with an -ide ending, and never put mono on the first element. CO2 is carbon dioxide and N2O5 is dinitrogen pentoxide.

What is the difference between naming ionic and covalent compounds?

Covalent (molecular) compounds of two non-metals use prefixes. Ionic compounds of a metal and a non-metal never use prefixes; the charges set the ratio, so NaCl is sodium chloride, not sodium monochloride.

How do you name acids?

Binary acids use hydro- and -ic: HCl(aq) is hydrochloric acid. Oxyacids are named from the polyatomic ion: -ate ions give -ic acids (sulfate, sulfuric acid) and -ite ions give -ous acids (sulfite, sulfurous acid).

What grade is this naming covalent compounds worksheet for?

It is written for Grade 11 chemistry (Ontario SCH3U) and suits any introductory high school chemistry course.

More Free Grade 11 Chemistry Resources

Ready to practise? Download the free naming covalent compounds worksheet PDF (use the Download button above), print it double-sided, and keep the answer key pages for marking.

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