Topic 6 - Formulae and equations

• Physics
• Secondary Education
• Age 12,13

27 October 2025

Topic 6 - Formulae and Equations

We are learning to:

• State the formulae of the elements and compounds
• Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation, or from the charges on the ions
• Deduce the formula of a simple compound from the relative numbers of atoms present in a model or a diagrammatic representation

How are you today?

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Why is it not acceptable to balance the equation 

Na + Cl2 → NaCl

by changing the formula of NaCl to NaCl2?

Q4D-Day 

Activity 1 - Formulae of Elements

• State the formulae of the elements and compounds

• State the formulae of the elements and compounds

NaCl

• State the formulae of the elements and compounds

NaCl

CO2

• State the formulae of the elements and compounds

NaCl

CO2

Al2(SO4)3

• State the formulae of the elements and compounds

Activity 2 - Formulae of Compounds

• State the formulae of the elements and compounds

Sodium sulfide

Valency

Symbol

Formula

• Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation, or from the charges on the ions

Calcium oxide

Valency

Symbol

Formula

• Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation, or from the charges on the ions

Activity 3 - Working out the formula of IONIC compounds

• Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation, or from the charges on the ions

Why is it not acceptable to balance the equation 

Na + Cl2 → NaCl

by changing the formula of NaCl to NaCl2?

Q4D-Day 

Why is it not acceptable to balance the equation
Na + Cl₂ → NaCl
by changing the formula of NaCl to NaCl₂?