The shape of the lesson
By the end of the lesson, learners can
- Transition metals versus Group I: Compare a typical transition metal, iron, with a Group I metal, sodium.
- Colours, catalysts and oxidation numbers: These properties explain many uses of the transition elements.
- High density and high melting point.
- Coloured compounds.
- Catalysts (as the element or a compound).
- Extended: variable oxidation numbers.
One picture every idea returns to
The transition elements are metals with high densities and high melting points. They form coloured compounds, and the elements and their compounds often act as catalysts. Extended: transition elements have ions with variable oxidation numbers, such as iron(II), Fe2+, and iron(III), Fe3+.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, The hard-working middle.. Iron, copper, nickel and their neighbours sit in the central block of the table. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Transition metals versus Group I | Compare a typical transition metal, iron, with a Group I metal, sodium. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Colours, catalysts and oxidation numbers | These properties explain many uses of the transition elements. | Quiz-Quiz-Trade |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 14 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Colours, catalysts and oxidation numbers, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Quiz-Quiz-Trade
Each student holds a card with a question on the front and the answer on the back. They pair up, quiz each other, coach if needed, trade cards and find a new partner. Three rounds covers the whole set.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| "Coloured compounds" is about the compounds, not the metals: copper metal is pink-brown, but the property that marks a transition element is that its compounds and solutions are coloured. | And a catalyst is not used up, so "iron reacts in the Haber process" is wrong. |
Transition elements: worksheet
6 questions, 14 marks. Written in the style of the papers; no past paper question is reproduced.
State four properties of transition elements that are not shown by Group I metals.
Name a transition element or compound used as a catalyst, and the process in which it is used.
Element M melts at 1455 °C, has a density of 8.9 g/cm3 and forms a green sulfate. Suggest, with reasons, whether M is a transition element or a Group I element.
(Extended) Give the formulae of iron(II) oxide and iron(III) oxide, and state what they show about iron.
Suggest why transition metals rather than Group I metals are used to build bridges and machinery.
State the colour of a solution containing (a) copper(II) ions and (b) iron(III) ions.
Answer key and marking notes
- High density.
- High melting point.
- Form coloured compounds.
- Act as catalysts (Extended: variable oxidation numbers).
- Iron: the Haber process (or vanadium(V) oxide: the Contact process; nickel: hydrogenation of oils).
- One mark for the catalyst, one for the matching process.
- A transition element.
- It has a high melting point and a high density and forms a coloured compound, all typical of transition elements.
- FeO and Fe2O3.
- Iron has variable oxidation numbers (+2 and +3).
- Transition metals are hard, strong and dense with high melting points.
- Group I metals are soft and react rapidly with water and air.
- (a) blue
- (b) orange-brown (yellow-brown)
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
The diagram shows an outline of part of the Periodic Table with five elements labelled A to E. Which labelled element is most likely to form a coloured sulfate and to act as a catalyst?
- AC
- BA
- CD
- DE
Vanadium(V) oxide is used in the Contact process. What is its role?
- AIt is a catalyst: it speeds up the reaction and is not used up.
- BIt is a reactant that is converted into sulfuric acid.
- CIt absorbs the product so that more can form.
- DIt slows the reaction down to make it safer.
Data for four metals are given. Which metal is most likely to be a transition element?
- Amelting point 1085 °C, density 8.9 g/cm3
- Bmelting point 98 °C, density 0.97 g/cm3
- Cmelting point 63 °C, density 0.86 g/cm3
- Dmelting point 650 °C, density 1.7 g/cm3
A student dissolves a solid in water and obtains a pale green solution. Which metal ion is most likely to be present?
- AFe2+
- BFe3+
- CCu2+
- DNa+
A student writes: "Iron is used up in the Haber process because it reacts with nitrogen to make ammonia." Which statement is correct?
- AIron is a catalyst, so the same mass of iron remains at the end.
- BIron is a reactant, so it must be replaced after each batch of ammonia.
- CIron reacts with hydrogen, not nitrogen, to make ammonia.
- DIron is added to raise the melting point of the mixture.
Chromium forms the green oxide Cr2O3. What is the oxidation number of chromium in this compound?
- A+3
- B+2
- C+6
- D−3
A pale green solution of iron(II) sulfate is left open to the air and slowly turns orange-brown. What has happened to the iron ions?
- AFe2+ ions have been oxidised to Fe3+ ions.
- BFe3+ ions have been reduced to Fe2+ ions.
- CThe iron ions have been turned into iron metal.
- DThe iron ions are unchanged; the sulfate ions have become coloured.
Manganese forms two oxides, MnO and MnO2. What are the oxidation numbers of manganese in these two oxides?
- A+2 in MnO and +4 in MnO2
- B+1 in MnO and +2 in MnO2
- C+2 in both oxides
- D−2 in MnO and −4 in MnO2
Quiz key
Element C is in the central block of Period 4, so it is a transition element; these form coloured compounds and often act as catalysts. A is a Group I metal, whose compounds are white and whose solutions are colourless. D is a noble gas and is unreactive. E is a halogen, a non-metal.
Vanadium(V) oxide is a catalyst: it increases the rate of the reaction between sulfur dioxide and oxygen and is chemically unchanged at the end. It is not a reactant, so it is not converted into the product. Absorbing the product is a separate stage of the process, and a catalyst speeds a reaction up rather than slowing it down.
Transition elements have high melting points and high densities; 1085 °C and 8.9 g/cm3 are the values for copper. The metals melting at 98 °C and 63 °C with densities below 1 g/cm3 are sodium and potassium, both Group I metals. The metal melting at 650 °C with density 1.7 g/cm3 is magnesium, a Group II metal: its melting point and density are both far lower than a typical transition element.
Iron(II) compounds give pale green solutions. Iron(III) solutions are orange-brown, copper(II) solutions are blue, and sodium ions, from a Group I metal, give colourless solutions.
Iron is the catalyst in the Haber process: it speeds up the reaction between nitrogen and hydrogen but is not used up, so its mass is unchanged. Ammonia is made from nitrogen and hydrogen only, so iron is not a reactant with either gas, and it is not there to change any melting point.
Three O2− ions give a total of −6, so the two chromium ions must total +6, which is +3 each: chromium(III) oxide. +6 is the total for both chromium atoms, not the value for one. +2 would give CrO, and a metal in an oxide has a positive, not a negative, oxidation number.
Iron has variable oxidation numbers. Pale green is typical of iron(II) and orange-brown of iron(III), so Fe2+ has lost an electron to become Fe3+: an increase in oxidation number, which is oxidation. The reverse change would go from orange-brown to green. Iron metal would appear as a grey solid, not a coloured solution, and sulfate ions are colourless.
In MnO one oxygen at −2 is balanced by manganese at +2. In MnO2 two oxygens total −4, so manganese is +4. This shows the variable oxidation numbers of transition elements. Reading the subscripts as the oxidation numbers gives +1 and +2, which ignores the charge on oxygen; the same value in both oxides could not balance two different formulae; and the metal, not oxygen, carries the positive value.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.