Year 8 Science · Unit 2 · Lesson 20
Challenge Worksheet
Learning Goals
Find the mistake
A student wrote this answer
"Chemical compounds are easy to name. For the formula H₂S, I would call it 'hydrogen sulphur' because it contains hydrogen and sulphur. For MgO I'd call it 'magnesium oxygen'. The formula NaCl must be 'chlorine sodium' because I write the second element first when naming. And CaF₂ would be 'calcium fluorine', simple."
1. List every naming mistake the student made. There are at least four errors, find them all. For each one, identify which compound is affected.
2. Write the correct IUPAC name for each of the four compounds: H₂S, MgO, NaCl, CaF₂.
3. Explain the -ide naming rule in your own words. Why do you think scientists agreed to use a fixed rule like this, rather than letting each chemist choose their own name?
1. A student correctly names AlCl₃ as "aluminium chloride" but then incorrectly names KBr as "potassium bromine". Identify the single error and write the correct name. Then explain the rule they forgot to apply.
2. Sodium chloride (NaCl) is found in Australian saltpans like Kati Thanda–Lake Eyre in South Australia. Calcium carbonate (CaCO₃) is the main mineral in limestone forming the Nullarbor caves. CaCO₃ has three elements, does the -ide rule still apply? Explain why or why not, and give the formal name if you can.
Wrap Up
In one sentence, what was the main idea of this lesson?