Playbook
Transition and Inner Transition Elements
76 q - 1.75/paper - 4% HARD. Configurations, the spin-only moment and lanthanoid contraction.
- Questions in the bank
- 76
- q/paper (2024–25 papers)
- 1.75
- Tagged HARD
- 4%
- Subtopics
- 5
Strand: Recall
When you’ll see it
A d- or f-block element's configuration, oxidation states, colour, magnetic moment, or a lanthanoid trend.
How this chapter is tested
76 q at 1.75 a paper, 4% HARD. Configurations carry the chapter — and chromium (3d⁵4s¹) and copper (3d¹⁰4s¹) break the filling pattern. Colour comes from unpaired d electrons, so Sc³⁺, Ti⁴⁺ and Zn²⁺ are colourless.
The spin-only formula μ = √(n(n + 2)) BM turns unpaired electrons into a moment (Mn²⁺, five unpaired, 5.92 BM). Lanthanoids (27 q): the lanthanoid contraction and +3 as the common oxidation state.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Configurations
3d filling with the Cr and Cu exceptions; ions lose 4s electrons first.
Magnetism
μ = √(n(n + 2)) BM: n = 1 → 1.73, 2 → 2.83, 3 → 3.87, 4 → 4.90, 5 → 5.92.
Colour
Coloured if there are unpaired d electrons (d¹-d⁹); d⁰ and d¹⁰ ions are colourless.
Lanthanoids
Contraction across the series; +3 common, Ce⁴⁺ and Eu²⁺ as exceptions.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Removing 3d before 4s
Fe²⁺ is 3d⁶, not 3d⁴4s²: the 4s electrons leave first.
Zn²⁺ as coloured
Zn²⁺ is d¹⁰, so colourless and diamagnetic.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Transition and Inner Transition Elements notesDrill every transition and inner transition elements question
76 questions from the bank, scoped to 5 bundled subtopics.
Drill one subtopic at a time
The 5 subtopics this playbook covers, in catalog order.
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