Starter quiz
- Ions form through the loss or gain of ...
- 'electrons' ✓
- When a nitrate ion forms, it gains one electron. What charge does a nitrate ion have?
- 2+
- 2–
- 1+
- 1– ✓
-
- True or false? Non–metal atoms gain electrons to become more stable, negatively charged ions.
- True ✓
- False
- Which of the following statements about ammonium nitrate, NH₄NO₃, are correct?
- The substance contains three elements. ✓
- The formula contains two nitrogen atoms. ✓
- The substance contains three oxygen atoms.
- The ratio of hydrogen to oxygen in the formula is 3 : 4.
-
- Match the following terms to the correct definitions.
- ionic bond⇔The electrostatic force of attraction between oppositely charged ions. ✓
- lattice⇔The regular arrangement of atoms or ions in a 3D space. ✓
- ion⇔Atom or molecule with a charge due to the gain or loss of electrons. ✓
- Magnesium chloride is an ionic compound. Which of the following statements does not describe magnesium chloride?
- It contains Mg²⁺ and Cl⁻ ions.
- It forms simple molecules. ✓
- It forms a giant lattice.
- One Mg²⁺ ion is attracted to two Cl⁻ ions.
-
Exit quiz
- Match the following key terms to the correct definition.
- empirical formula⇔Simplest whole number ratio of atoms of each element in a compound. ✓
- molecular formula⇔Shows the actual number of atoms of each element in a compound. ✓
- polyatomic ions⇔Ions made of more than one type of atom. ✓
- –ide compounds⇔Name ending for a compound with a metal and singular non–metal. ✓
- –ate compounds⇔Name ending for a compound with 3 or more elements, one being oxygen. ✓
- The molecular formula for hydrogen peroxide is H₂O₂. What is its empirical formula?
- 'HO' ✓
- Which of the following are examples of ionic compounds with names ending with –ide?
- NaCl ✓
- MgSO₄
- H₂O
- CaO ✓
-
- Which of the following are examples of polyatomic ions?
- Na⁺
- SO₄²⁻ ✓
- Cl⁻
- Cu(NO₃)₂
- CO₃⁻ ✓
-
The image shows the ionic compound lead(II) chloride. What is the empirical formula for lead(II) chloride?- PbCl
- PbCl₂ ✓
- Pb₂Cl
-
- The ammonium ion has the formula: NH₄⁺. Sulfate ions have the formula: SO₄²⁻. What is the formula for ammonium sulfate?
- NH₄⁺SO₄²⁻
- NH₄SO₄
- NH₄(SO₄)₂
- (NH₄)₂SO₄ ✓
-
Worksheet
Presentation
Video
Lesson Details
Key learning points
- An empirical formula is the simplest whole number ratio of atoms of each element in a compound.
- The formula of an ionic compound is an empirical formula, as there is no definite quantity of each ion.
- Ionic compounds ending with "–ide" only contain a metal and a non–metal ion.
- Polyatomic ions are ions that are made up of more than one type of atom.
- Ionic compounds ending with "–ate" always contain at least three elements, one of which is oxygen.
Common misconception
Using ionic charges to determine the empirical formulae, especially with polyatomic ions. Standard notation is difficult and confusing, e.g. when to use superscripts, subscripts or brackets.
At this stage, pupils will need to just learn the the formulae of the polyatomic ions and accept that a full explanation will come later in their chemistry learning. Provide pupils with plenty of practice of writing and using ionic formulae.
Keywords
Empirical formula - The simplest whole number ratio of atoms of each element in a compound.
Polyatomic ions - Ions that are made up of more than one type of atom.
"–ide" - The name ending for a compound with a metal and non–metal present, for example, potassium iodide (KI).
"–ate" - The name ending for a compound with three or more elements present (one of which is oxygen), for example, potassium sulfate (K₂SO₄).