Class 12 Chemistry - BIHAR
The d- and f-Block Elements
The d- and f-Block Elements chapter in Class 12 Chemistry explores the chemistry of transition and inner-transition elements found in groups 3-12 and the periodic table's bottom rows. Students learn about electronic configurations, variable oxidation states, magnetic properties, color formation, and alloy creation for d-block (transition metals), alongside the lanthanoid and actinoid contractions and oxidation states for f-block elements. This chapter is vital for the Bihar Board (BSEB) exams as it consistently yields high-scoring conceptual questions, reasoning-based problems, and IUPAC naming/coordination link questions, making a thorough understanding of trends and properties essential.
Start Learning FreeKey Concepts
Transition Elements
Elements that have partly filled d-orbitals in their ground state or in any of their oxidation states, generally classified as groups 3 to 12.
Lanthanoid Contraction
The steady decrease in atomic and ionic radii of lanthanoids with an increasing atomic number, caused by the poor shielding effect of 4f electrons.
Magnetic Moment
Calculated using the spin-only formula mu = sqrt(n(n+2)) BM, where n represents the number of unpaired electrons in the d-orbital.
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, structures, and oxidizing properties in acidic/basic mediums are heavily tested in board exams.
Important Formulas
Board Exam Info
In the Bihar Board (BSEB) Class 12 Chemistry exam, this chapter typically carries around 5 to 7 marks. Questions frequently include objective (MCQ) types, short-answer reasoning questions (such as why transition metals act as catalysts or exhibit variable oxidation states), and long-answer descriptive questions on the manufacture and properties of KMnO4 or K2Cr2O7.
Frequently Asked Questions
Why do transition elements form colored ions?
They form colored ions due to the d-d electron transition, where electrons absorb light in the visible region to jump from lower to higher d-orbitals.
What is Lanthanoid Contraction and what are its consequences?
It is the gradual decrease in size of lanthanoid ions. Its main consequence is that the atomic radii of the second and third transition series elements are very similar.
Why are Zn, Cd, and Hg not considered true transition elements?
Because they have completely filled d-orbitals (d10) in their ground state as well as in their common oxidation states, lacking partly filled d-orbitals.
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