Nomenclature Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Nomenclature.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

The systematic method for naming chemical compounds according to IUPAC rules, ensuring that every compound has exactly one correct name and every name points to exactly one compound.

Chemistry has a naming system so that every compound gets exactly one name and every name points to exactly one compound — like a universal address system.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Nomenclature starts by identifying valence electrons, likely charges or sharing, and the structure that follows.

Common stuck point: Students often know a formula related to nomenclature but skip the recognition step: Am I explaining a substance by electron behavior, bond type, molecular shape, polarity, or attractions between particles? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Am I explaining a substance by electron behavior, bond type, molecular shape, polarity, or attractions between particles?

Worked Examples

Example 1

easy
Name the following ionic compounds: (a) NaCl, (b) CaO\text{CaO}, (c) FeCl3\text{FeCl}_3.

Answer

(a) sodium chloride, (b) calcium oxide, (c) iron(III) chloride\text{(a) sodium chloride, (b) calcium oxide, (c) iron(III) chloride}

First step

1
(a) Na = sodium, Cl = chloride → sodium chloride.

Full solution

  1. 2
    (b) Ca = calcium, O = oxide → calcium oxide.
  2. 3
    (c) Fe can have multiple charges. With 3 Cl−^-, Fe must be +3+3. → iron(III) chloride.
For ionic compounds, name the cation first and then the anion (with -ide ending). Transition metals require Roman numerals to indicate their charge since they can form multiple ions.

Example 2

medium
Name these covalent compounds: (a) CO2\text{CO}_2, (b) N2O4\text{N}_2\text{O}_4, (c) PCl5\text{PCl}_5.

Example 3

medium
Write the formula for aluminum sulfate.

Example 4

medium
Give the formula for chromium(III) oxide.

Example 5

hard
Name Hg2Cl2\text{Hg}_2\text{Cl}_2 (note: mercury(I) is a dimer Hg22+\text{Hg}_2^{2+}).

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Write the chemical formula for: (a) potassium bromide, (b) aluminum oxide.

Example 2

hard
Name the following compounds: (a) FeCl3\text{FeCl}_3, (b) N2O5\text{N}_2\text{O}_5, (c) Cu2O\text{Cu}_2\text{O}. Explain the naming convention used for each.

Example 3

easy
Name the compound NaCl.

Example 4

easy
Name the compound MgOMgO.

Example 5

easy
Name the covalent compound CO2CO_2.

Example 6

easy
Name FeCl3FeCl_3.

Example 7

easy
Name CaCl2CaCl_2.

Example 8

easy
Name the covalent compound N2O4N_2O_4.

Example 9

easy
Name K2SK_2S.

Example 10

easy
Name the compound Na2SO4Na_2SO_4.

Example 11

medium
Name Fe2O3Fe_2O_3 including the Roman numeral.

Example 12

medium
Name Cu2OCu_2O.

Example 13

medium
Distinguish: SO42−SO_4^{2-} vs SO32−SO_3^{2-} in naming.

Example 14

medium
Name the acid H2SO4H_2SO_4.

Example 15

medium
Name the acid H2SO3H_2SO_3.

Example 16

medium
Why is PCl3PCl_3 named with prefixes but AlCl3AlCl_3 is not?

Example 17

medium
Name Pb(NO3)2Pb(NO_3)_2 with the Roman numeral.

Example 18

medium
Name P2O5P_2O_5.

Example 19

medium
Name SO3SO_3 (covalent compound).

Example 20

challenge
Give the formula from the name iron(III) sulfate.

Example 21

challenge
Give the formula from the name dinitrogen pentoxide.

Example 22

challenge
Name NH4NO3NH_4NO_3 (contains two polyatomic ions).

Example 23

easy
Name the ionic compound LiF\text{LiF}.

Example 24

easy
Name the compound BaCl2\text{BaCl}_2.

Example 25

easy
Name the covalent compound SF6\text{SF}_6.

Example 26

easy
Name the compound AgCl\text{AgCl}.

Example 27

easy
Name HF(aq)\text{HF}(aq).

Example 28

medium
Name the compound CuSO4\text{CuSO}_4.

Example 29

medium
Name Mg(OH)2\text{Mg(OH)}_2.

Example 30

medium
Name HNO3\text{HNO}_3.

Example 31

medium
Name HNO2\text{HNO}_2.

Example 32

medium
Name ZnCO3\text{ZnCO}_3.

Example 33

medium
Name Sn(NO3)4\text{Sn(NO}_3\text{)}_4.

Example 34

medium
Name ClF3\text{ClF}_3.

Example 35

medium
Name KMnO4\text{KMnO}_4.

Example 36

medium
Name NaHCO3\text{NaHCO}_3.

Example 37

medium
Name HClO4\text{HClO}_4.

Example 38

hard
Write the formula for ammonium phosphate.

Example 39

hard
Write the formula for iron(II) phosphate.

Example 40

hard
Why is the name 'iron oxide' considered ambiguous?

Example 41

hard
Name Co2(SO4)3\text{Co}_2(\text{SO}_4)_3.

Example 42

challenge
Give the IUPAC name for H3PO3\text{H}_3\text{PO}_3, where the anion PO33−\text{PO}_3^{3-} ends in '-ite'.
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Related Concepts

Formula WritingIon

Background Knowledge

These ideas may be useful before you work through the harder examples.

formula writingion