The d- and f-Block Elements
Class 12 · Chemistry
4 ideas in Class 12 Chemistry, explained in plain words, with games and quizzes to practise.
Position, Config and Periodic Trends
Part of: Transition Trends and Oxidation States
The d-block fills d orbitals across Groups 3 to 12, with chromium and copper stealing an s electron for half- and full-shell stability. Zinc, cadmium and mercury miss transition status since their ions keep full d shells, while radii shrink across rows and melting points peak mid-series.
Why it matters. Steel, coins and catalysts all exploit these trends. Forcing expected configs, or calling zinc a transition metal, breaks every property answer.
Formulas
- Cr: 3d5 4s1; Cu: 3d10 4s1
- Transition needs incomplete d in atom or ion
- Radii fall across, then rise at the end
Key words
- Transition element
- : Element with partly filled d orbitals as atom or ion.
- d-block
- : Groups 3 to 12 where d orbitals fill.
- Lanthanoid contraction
- : Steady shrink across f-block making 4d and 5d sizes match.
Try it in two minutes
- Write the config, checking Cr and Cu exceptions.
- Test transition status on ions, not just atoms.
- Track radii, melting and ionisation across the row.
Try at home. Write configs for Cr, Cu, Zn2+ and Ag and test each.
Oxidation States and Electrode Potentials
Part of: Transition Trends and Oxidation States
Transition metals span many states since s and d electrons both bond, with +2 most common and manganese reaching +7. Stability follows half- and full-shells: Cr2+ reduces toward d3, Mn3+ oxidises toward d5, and Cu+ splits into Cu2+ and Cu in water, while fluorine and oxygen alone stabilise the highest states.
Why it matters. Oxidisers, batteries and steel-making all pick states by stability. Expecting one fixed valency like main groups breaks every equation.
Formulas
- Common first-row state: +2
- Manganese spans +2 to +7
- Only F and O stabilise top states
Key words
- Oxidation state
- : Charge assigned assuming ionic bonds.
- Disproportionation
- : One state splitting into higher and lower states.
- Standard potential
- : Reduction tendency measured against hydrogen.
Try it in two minutes
- List possible states from s plus d electrons.
- Check half- and full-shell landing spots.
- Rank oxidising and reducing strength by landing.
Try at home. Write states for Mn from +2 to +7 with one example each.
Colour, Magnetism, Catalysis and Alloys
Part of: Properties, Compounds and f-Block
Partially filled d orbitals split in ligands, absorbing visible light for colour, while unpaired spins give magnetic moments of root n(n+2) Bohr magnetons. Variable states and surfaces make great catalysts, similar sizes blend into alloys, and small highly charged ions grip ligands into complexes.
Why it matters. Pigments, magnets, Haber iron and steel all use these traits. Calling d10 ions coloured, or missing the spin-only formula, breaks identification answers.
Formulas
- Moment: mu = sqrt(n(n + 2)) BM
- Colour needs incomplete d orbitals
- Catalysts use variable states plus surfaces
Key words
- d-d transition
- : Electron hop between split d orbitals absorbing visible light.
- Spin-only moment
- : Magnetic moment from unpaired spins, root n(n+2) BM.
- Alloy
- : Homogeneous metal blend with improved properties.
Try it in two minutes
- Count unpaired electrons for colour and magnetism.
- Apply root n(n+2) for the moment.
- Match catalysts and alloys to variable states and sizes.
Try at home. Order Ti3+, Cu2+, Zn2+ by colour depth.
Important Compounds and f-Block
Part of: Properties, Compounds and f-Block
Potassium permanganate from pyrolusite and dichromate from chromite are powerful oxidisers with manganese at +7 and chromium at +6. The f-block fills 4f and 5f rows, mostly +3 through lanthanoid contraction, with actinoids showing wider states and radioactivity.
Why it matters. Titrations, leather tanning and nuclear fuel all use these chemicals. Misstating the central oxidation state ruins every redox balance.
Formulas
- Mn in KMnO4 is +7
- Cr in K2Cr2O7 is +6
- Lanthanoids mostly +3; Ce shows +4
Key words
- Permanganate
- : MnO4- ion with manganese at +7, a strong oxidiser.
- Dichromate
- : Cr2O7 ion with chromium at +6, a strong oxidiser.
- Lanthanoid contraction
- : Steady size shrink across the 4f row.
- Actinoids
- : Radioactive 5f row with varied oxidation states.
Try it in two minutes
- Assign oxidation states to Mn and Cr centres.
- Name the ore behind each salt.
- Contrast 4f with 5f behaviour.
Try at home. Balance one permanganate titration half-equation.
What your child will practise
- Colour, Magnetism, Catalysis and Alloys: Jungle Quick Fire (Quick Fire)
- Colour, Magnetism, Catalysis and Alloys: Ocean Quest (Flip and Match)
- Important Compounds and f-Block: Candy Puzzle (Clue Puzzle)
- Oxidation States and Electrode Potentials: Desert Quick Fire (Quick Fire)
- Position, Config and Periodic Trends: Space Puzzle (Clue Puzzle)
- Quiz: Colour, Magnetism, Catalysis and Alloys (8 questions)
- Quiz: Important Compounds and f-Block (8 questions)
- Quiz: Oxidation States and Electrode Potentials (8 questions)
- Quiz: Position, Config and Periodic Trends (8 questions)