Transition Metals – SS3 Chemistry Lesson Note (First Term)

Transition metals are d-block elements whose atoms or common ions have partially filled d orbitals.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define transition metals and list the elements of the first transition series.
2. Write the electronic configurations of the first series, including chromium and copper.
3. Explain the general properties of transition metals, with examples.
4. Describe the steps in the extraction of tin from cassiterite.
5. State the uses of tin.

Instructional techniques

• Identification: pupils pick out the first series on the periodic table.
• Explanation: the teacher explains properties and the extraction steps.
• Questions and answers: short oral checks after each section.
• Demonstration: show coloured compounds or samples of tin, iron and copper.
• Videos from source: short clips on tin mining and smelting.

Instructional materials

• Videos
• Loudspeaker
• Textbook
• Pictures
• Periodic table chart

What are transition metals?

Transition metals are elements in the d block of the periodic table with partially filled d orbitals in their atoms or common ions.

• Position: they lie between Group 2 and Group 13, in the middle of the periodic table.
• Examples: iron, copper, manganese, chromium, nickel and zinc.
• Strict definition: a transition element forms at least one ion with a partially filled d subshell.
• Scandium and zinc: they sit in the 3d block and are listed in the first series, but Sc³⁺ has no d electrons and Zn²⁺ has a full d subshell.
• Tin: tin is a Group 14 metal, not a d-block transition metal. It is studied alongside this topic.

What is the first transition series?

The first transition series is the set of ten elements from scandium (Sc) to zinc (Zn), in which the 3d orbitals are being filled.

• Elements in order: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.
• Atomic numbers: 21 (Sc) to 30 (Zn).
• Filling order: the 4s orbital fills before 3d, but 4s electrons are lost first when ions form.

Below is the electronic configuration of transition metals.

What are the electronic configurations of the first series?

Each element of the first series has the argon core, [Ar], followed by 3d and 4s electrons.

• Chromium: one 4s electron moves into 3d to give a half-filled 3d subshell, which is stable.
• Copper: one 4s electron moves into 3d to give a completely filled 3d subshell, which is stable.

What are the general properties of transition metals?

The general properties of transition metals are variable oxidation states, complex ion formation, coloured compounds, catalytic activity, magnetism, high melting points, high density, malleability and ductility.

1. Variable oxidation states: the 3d and 4s electrons have similar energies, so different numbers of electrons can be lost. Iron forms Fe²⁺ and Fe³⁺.
2. Formation of complex ions: they bind ligands such as water, ammonia and chloride ions to form complex ions. Copper(II) with ammonia gives a deep blue complex.
3. Coloured compounds: their compounds absorb some wavelengths of light because of electron changes in the d orbitals.
4. High melting and boiling points: they have strong metallic bonding, so they melt at higher temperatures than Group 1 and Group 2 metals.
5. Magnetic properties: unpaired d electrons give paramagnetism. Iron, cobalt and nickel are ferromagnetic.
6. Catalytic activity: they and their compounds speed up reactions and take part in redox changes.
7. High density: their atoms are heavy and closely packed, so the metals are dense.
8. Malleability and ductility: they can be hammered into sheets and drawn into wires.

What are examples of coloured compounds and catalysts?

What are common oxidation states of transition metals?

• Iron: +2 and +3.
• Copper: +1 and +2.
• Chromium: +2, +3 and +6.
• Manganese: +2 up to +7, as in MnO₄^–.

How do transition metals differ from Group 1 metals?

Group 1 metals (such as sodium and potassium) are soft, reactive s-block metals. Transition metals are harder, less reactive d-block metals.

How is tin extracted?

Tin is extracted from its ore, cassiterite (SnO₂), by concentrating the ore and reducing it with carbon.

1. Mining: cassiterite is mined from deposits in the Earth’s crust, for example on the Jos Plateau.
2. Concentration: the ore is crushed and ground to concentrate the tin-bearing minerals.
3. Gravity separation: heavy cassiterite is separated from lighter minerals using gravity.
4. Smelting: the concentrate is heated with carbon in a furnace to reduce tin(IV) oxide to crude tin.
5. Refining: impurities are removed from the crude tin by liquation or electrolysis.
6. Casting: the refined tin is cast into ingots for sale.

What is the equation for the smelting of tin?

Carbon reduces tin(IV) oxide to tin metal and carbon monoxide.

• Equation: SnO₂ + 2C → Sn + 2CO
• Reducing agent: carbon, which removes oxygen from the oxide.
• Product: crude tin, which still contains impurities such as iron.

What are liquation and electrolysis in refining?

• Liquation: crude tin is heated on a sloping hearth; tin melts and flows away, leaving higher-melting impurities behind.
• Electrolysis: crude tin is the anode and pure tin collects at the cathode.

What are the uses of tin?

Tin is a soft, silvery metal that resists corrosion, so it is used for coating, soldering and making alloys.

• Solder: tin is a main part of solder, which joins wires and electronic components.
• Tinplate: steel is coated with a thin layer of tin to stop rusting, as in food and drink cans.
• Bronze: bronze is an alloy of copper and tin, known for strength and resistance to corrosion.
• Other alloys: tin is also alloyed with other metals to give useful properties, as in pewter.
• Chemicals: some tin compounds are used as catalysts and stabilisers.

Evaluation

1. Discuss the extraction of tin.
2. Write down four uses of tin.
3. What are transition metals?
4. Write down the electronic configuration of scandium and titanium.
5. Why do chromium and copper have unusual configurations?

Assignment

Write a short note on the first transition series that includes these parts:

• Four general properties of transition metals.
• The first and last elements of the series.
• One transition metal with variable oxidation states, and the oxidation states it can have.