Testing

Quick Recap: Naming Chemistry the IUPAC Way

Before we test ourselves, let's remind ourselves why nomenclature matters. Chemists all over the world need a system so that a formula or name means exactly the same thing no matter what language you speak. This job belongs to IUPAC (International Union of Pure and Applied Chemistry), which sets out clear rules for naming both inorganic ions/compounds and organic molecules (Talbot, p.172).

For organic compounds, IUPAC names are built from three parts (Talbot, p.289):

• Stem – shows the number of carbon atoms in the longest unbranched (parent) chain (e.g., meth-, eth-, prop-, but-)
• Stem ending – shows whether the chain is saturated or unsaturated (-ane, -ene, -yne)
• Suffix and prefixes – the suffix shows the principal functional group, while prefixes (in alphabetical order) show the position of any substituent groups

For inorganic compounds, remember the key rules:

• Simple ionic compounds: cation name + anion name (e.g., sodium chloride = NaCl)
• Transition metal compounds need a Roman numeral to show oxidation state (e.g., iron(II) oxide = FeO, iron(III) oxide = Fe₂O₃)
• Polyatomic ions have fixed names you must memorise (e.g., CO₃²⁻ = carbonate, NO₃⁻ = nitrate, SO₄²⁻ = sulfate)

Worked Example

Name C₃H₆:

1. Count carbons in the longest chain → 3 carbons → stem "prop-"
2. Check saturation → one C=C double bond → ending "-ene"
3. Combine → propene

Name Fe₂O₃:

1. Identify the cation → iron, but iron has variable oxidation states
2. Work out the charge on Fe using the oxide charge (O²⁻ × 3 = 6−, so Fe must total 6+, meaning each Fe is 3+)
3. Combine → iron(III) oxide

Practice Set – Test Yourself!

Try these five short questions without looking back at your notes. Check your answers afterwards.

1. Name the compound with formula CuSO₄.
2. Give the IUPAC name for CH₃CH₂CH₂OH.
3. What functional group suffix would you use for a molecule containing a C=O bond at the end of a carbon chain (an aldehyde)?
4. Name the ionic compound Ca₃(PO₄)₂.
5. Identify the stem and stem ending needed to name C₄H₈ (one double bond, straight chain).

Key Takeaways

• IUPAC nomenclature exists to make chemical communication unambiguous and consistent worldwide (Talbot, p.172).
• Organic names combine a stem (carbon count), a stem ending (saturation), and suffixes/prefixes (functional groups and substituents) (Talbot, p.289).
• Inorganic names combine cation and anion names, with Roman numerals needed for transition metals with variable oxidation states.
• Practising both forwards (formula → name) and backwards (name → formula) builds real fluency for exams.

Answers

1. Copper(II) sulfate
2. Propan-1-ol
3. The suffix "-al" (e.g., propanal)
4. Calcium phosphate
5. Stem = "but-" (4 carbons), ending = "-ene" (contains a double bond) → butene