Class 12 Chemistry - GUJARAT
The d- and f-Block Elements
The d- and f-Block Elements chapter explores the chemistry of transition and inner-transition elements found in the middle and bottom of the periodic table. For GSEB Class 12 students, mastering this chapter is essential as it explains variable oxidation states, coloured ions, catalytic properties, and complex formation of transition metals. You will also study the lanthanoid and actinoid series, focusing particularly on lanthanoid contraction and its consequences. This high-weightage chapter frequently features direct conceptual questions, reasoning-based problems, and numericals on magnetic moments in the Gujarat Board examinations.
Start Learning FreeKey Concepts
Transition Elements (d-block)
Elements that have incompletely filled d-orbitals in their ground state or in any of their common oxidation states (general electronic configuration: (n-1)d¹⁻¹⁰ns¹⁻²).
Lanthanoid Contraction
The steady decrease in atomic and ionic radii of lanthanoids with increasing atomic number, caused by the poor shielding effect of 4f electrons.
Magnetic Moment
Calculated using the spin-only formula based on the number of unpaired electrons present in the d or f orbitals of the metal ion.
Interstitial Compounds
Compounds formed when small atoms like H, C, or N are trapped inside the crystal lattices of transition metals, making them hard and rigid.
KMnO₄ and K₂Cr₂O₇ Preparation
Important oxidizing agents whose preparation, structure, and chemical reactions with reducing agents are heavily tested in board exams.
Important Formulas
Board Exam Info
In the Gujarat (GSEB) Class 12 Chemistry board exam, this chapter typically carries around 4 to 6 marks. Questions usually include 1 mark objective or MCQ, a 2-mark reasoning question (such as why transition metals show variable oxidation states or colored ions), and a 3-mark conceptual or preparation-based question.
Frequently Asked Questions
Why do transition elements exhibit variable oxidation states?
Because the energy difference between (n-1)d and ns orbitals is very small, electrons from both can participate in bonding.
What are the consequences of lanthanoid contraction?
It leads to the similarity in size of elements belonging to the second and third transition series (e.g., Zr and Hf) and makes their separation difficult.
Why are transition metal compounds generally colored?
Due to d-d electronic transition, where electrons absorb visible light to jump from one d-orbital to another, reflecting complementary colors.
Learn The d- and f-Block Elements with Your AI Tutor
10 different ways to study this chapter. Free for 3 chapters per day.
Lecture
Key Points
Interactive
Quiz
Flashcards