Worksheets › Class 12 › The d- and f-Block Elements
Class 12 The d- and f-Block Elements worksheet
CBSE Chemistry. Configurations, oxidation states, magnetic moments, colour, KMnO₄ and K₂Cr₂O₇, lanthanoids. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
Transition elements have partly filled:
- p orbitals
- f orbitals only
- s orbitals only
- d orbitals in the atom or a common ion
Answer
(d) d orbitals in the atom or a common ion
- 2.
The ground-state electronic configuration of chromium (Cr, Z = 24) is:
- [Ar] 3d⁵ 4s¹
- [Ar] 3d⁶
- [Ar] 4s² 4p⁴
- [Ar] 3d³ 4s²
Answer
(a) [Ar] 3d⁵ 4s¹
a half-filled or filled 3d set is extra stable
- 3.
The electronic configuration of Ni²⁺ (Z of Ni = 28) is:
- [Ar] 3d⁷ 4s¹
- [Ar] 3d⁹
- [Ar] 3d⁸
- [Ar] 3d⁶ 4s²
Answer
(c) [Ar] 3d⁸
4s electrons are removed before 3d
Section B · short answer
- 4.
Why are transition metal ions usually coloured?
Answer
Their partly filled d orbitals split in the presence of ligands, and an electron absorbs visible light to jump to a higher d level (d–d transition); the colour seen is the complementary colour.
- 5.
Write the electronic configuration of Sc³⁺ (Z of Sc = 21), and find the number of unpaired electrons and the spin-only magnetic moment.
Answer
[Ar] 3d⁰; 0 unpaired; 0 BM (diamagnetic)
μ = √(n(n + 2)) BM
Section C · long answer
- 6.
Describe the preparation of potassium dichromate from chromite ore, with equations.
Answer
Chromite is fused with sodium carbonate in air: 4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ + 8CO₂. The yellow sodium chromate is acidified: 2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O. Adding KCl gives the less soluble orange K₂Cr₂O₇: Na₂Cr₂O₇ + 2KCl → K₂Cr₂O₇ + 2NaCl.
Fresh sheets for your child
In the app, every The d- and f-Block Elements sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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