Writing Chemical Formulas

Name:

Date:

📚 Part 1: Identify and Choose (Multiple Choice)

Success criteria: I can read element symbols and subscripts to choose the correct chemical formula. I can use charge information for simple ionic compounds.

Differentiation: Use a periodic table or element symbol chart if needed. Extension: explain why your chosen formula is correct using charges or atom counts.

1. What is the correct formula for sodium chloride?

NaCl

NaCl2

Na2Cl

NaClO

2. Which formula shows two hydrogen atoms and one oxygen atom?

H2O

H2O2

OH2

3. Magnesium forms Mg2+ and oxygen forms O2−. Which formula correctly represents magnesium oxide?

MgO

Mg2O2

MgO2

Mg2O

4. Which of these formulas contains a polyatomic ion?

CaCO3

✏️ Part 2: Short Answers & Application

Success criteria: I can write correct chemical formulas from names, balance a simple equation, and identify reactants and products. Extension: use empirical formula ideas to suggest molecular formulas.

5. Write the chemical formula for aluminium sulphate. _________

6. Write and balance the equation for: magnesium + oxygen → magnesium oxide

7. Identify the reactants and products in this equation: 2H2 + O2 → 2H2O

Reactants:

Products:

8. Extension / Challenge: A compound has empirical formula CH and a relative molecular mass ≈ 26. Suggest its molecular formula and show your reasoning in one line.