Course

A2 Chemistry: Transition Elements (9701)

Name: A2 Chemistry: Transition Elements (9701)
Price: 1499 BDT

One incomplete d subshell, and everything else follows from it. Find the second isomer on a square and fail to find it on a tetrahedron, then find out that a solution is the colour it does not absorb.

20 lessons1h 55mEnglish

What you'll learn

Apply the definition of a transition element to an ion, and explain why scandium and zinc fail it
Write the electron configuration of a 3d element and of its ions, including chromium and copper
Explain why 4s fills before 3d and is removed before 3d
Explain variable oxidation state from the closeness of the 4s and 3d energies
Work out a coordination number by counting coordinate bonds, and the charge on a complex ion
Deduce the shape and bond angles of a complex from its coordination number
Explain why a tetrahedral complex shows no cis-trans isomerism and a square planar one does
Write equations for ligand exchange, and say when the coordination number changes
Use a stability constant to compare two complexes and explain the chelate effect by entropy
Explain the origin of colour in a complex, and give the colour seen from the colour absorbed
Calculate ΔE from an absorption wavelength, in joules and in kilojoules per mole
Predict how ligand, oxidation state and coordination number change a colour
Carry out a manganate(VII) titration calculation and justify the choice of acid
Explain transition-metal catalysis, including the electrode-potential condition on the catalyst
Identify Cu(II), Fe(II), Fe(III) and Cr(III) from their reactions with NaOH and with aqueous ammonia
Explain Group 2 thermal stability and solubility trends as particle-level cause chains rather than memorised directions

Requirements

AS atomic structure: subshells, orbitals and electron configuration
AS redox: oxidation numbers, half-equations and titration calculations
A2 electrochemistry: standard electrode potentials and cell feasibility

Course content

20 lessons · 1h 55m

28.1 · The d block

One definition, applied as a test that two d-block elements fail. Then the electron configurations it rests on, and the variable oxidation states that follow.

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What makes a transition element

An incomplete d subshell in an ion, not in the atom. Scandium and zinc are in the d block and fail the test.

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Electron configurations of the 3d series

4s fills first and 4s empties first. Both follow from 3d dropping below 4s once it is occupied.

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Variable oxidation states

Why one element has six oxidation states and sodium has one, and why the highest states need oxygen.

28.2, 28.4-28.5 · Complex ions

Coordination number as a count of bonds, then the shapes it fixes, then a failed search for a second isomer on a tetrahedron. Ends on ligand exchange and how far it goes.

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Ligands and coordination number

A dative bond from a lone pair, and a coordination number that counts bonds rather than ligands.

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Shape and stereoisomerism

Six is octahedral and four is usually tetrahedral. Find the second isomer on a square, then fail to find it on a tetrahedron.

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Ligand exchange and stability

Ammonia keeps the coordination number at six and chloride drops it to four. Stability constants say how far the swap goes.

28.3 · Colour

A solution is the colour it does not absorb. The d-orbital splitting that decides which band goes missing, then the three things that move it.

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Why a complex is coloured

Ligands split the d orbitals, an electron absorbs a photon of exactly that gap, and what you see is everything else.

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What changes the colour

Ligand, oxidation state and coordination number, and nothing else. Ends with colour used as a measurement.

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Redox, catalysis and identification

The model put to work: a manganate(VII) titration, the electrode-potential condition a catalyst has to satisfy, and naming an unknown ion from two test tubes.

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Manganate(VII) titration

Its own indicator, sulfuric acid only, and a 1:5 ratio that comes from the electrons rather than from the formulae.

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Why transition metals catalyse

Reduced by one reactant and re-oxidised by the other, which only works if the catalyst sits between the two electrode potentials.

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Identifying the ions

The colour narrows it down and the behaviour in excess names it. Two of the precipitates are green.

Transition elements: exam question

One structured Paper 4 question across configuration, coordination number, a colour calculation and a redox titration.

27.1 · Group 2: two competing energy changes

Replace two memorised trends with two energy competitions: cation polarisation controls thermal stability, while lattice and hydration enthalpies compete in solution.

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Thermal stability: who distorts the anion?

Use ionic radius and polarising power to explain why carbonates and nitrates become harder to decompose down Group 2.

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Solubility: lattice against hydration

Explain opposite hydroxide and sulfate trends by comparing how lattice and hydration enthalpies change down the group.

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Group 2 extension: exam question

A concise Paper 4 comparison requiring both polarisation language and the lattice–hydration energy balance.

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