Class 12 Chemistry - TELANGANA
The d- and f-Block Elements
The d- and f-Block Elements chapter for Class 12 Telangana (TSBSE) students explores the chemistry of transition and inner-transition elements found in groups 3-12 and the bottom of the periodic table. You will learn about their electronic configurations, variable oxidation states, coloured ion formation, catalytic properties, and complex compound formation. Special attention is given to the lanthanoid and actinoid series, highlighting phenomena like lanthanoid contraction. Mastering this chapter is crucial for scoring high in board exams as it features frequently in conceptual reasoning questions, IUPAC naming of coordination-linked aspects, and comparative property evaluations.
Start Learning FreeKey Concepts
Transition Elements (d-Block)
Elements that have incompletely filled d orbitals in their ground state or in any of their oxidation states (general electronic configuration: (n-1)d^1-10 ns^1-2).
Variable Oxidation States
d-Block elements exhibit multiple oxidation states due to the very small energy gap between (n-1)d and ns orbitals, allowing electrons from both to participate in bonding.
Magnetic Properties
Most transition metal ions are paramagnetic due to the presence of unpaired electrons in their d orbitals, which increases with the number of unpaired electrons.
Lanthanoid Contraction
The steady decrease in atomic and ionic radii of lanthanoids with increasing atomic number, caused by the imperfect shielding of nuclear charge by 4f electrons.
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.
Important Formulas
Board Exam Info
In the Telangana (TSBSE) Class 12 Chemistry board examinations, this chapter typically carries around 4 to 6 marks. Questions usually include very short answer questions (VSAQ) on definitions, short answer questions (SAQ) explaining properties like coloured ions or catalytic behaviour, and reasoning-based questions regarding lanthanoid contraction and magnetic moments.
Frequently Asked Questions
Why do transition elements form coloured ions?
Transition metal ions absorb light from the visible region to promote an electron from one d-orbital to another (d-d transition), transmitting the complementary colour.
What is Lanthanoid Contraction and what are its consequences?
It is the progressive decrease in atomic/ionic radii across the lanthanoid series. Consequences include the similarity in size of 4d and 5d transition series elements (e.g., Zr and Hf).
Why are Zn, Cd, and Hg not considered true transition elements?
Because they have completely filled d-orbitals (d^10) in their ground state as well as in their common oxidation states, lacking typical transition properties.
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