Class 12 Chemistry d and f Block Elements Formula Sheet PDF

Ans. You can download the d- and f-Block Elements Class 12 Chemistry Formula Sheet PDF directly from this Collegedunia page. Both the Normal and HD versions are available and free.

Ans. Yes. This page reflects the current 2026-27 syllabus for Class 12 Chemistry. The d- and f-Block Elements chapter is fully retained in the new edition with no formula cuts; every relation in Sections 4.1 to 4.8 of the NCERT remains examinable.

Ans. The Formula Sheet PDF runs approximately 8 pages and covers the master formula table, symbol glossary, magnetic-moment quick cards, trend table, when-to-use decision tree, and four common numerical pattern templates.

Ans. The spin-only magnetic moment is given by μ = √n(n+2) Bohr Magneton, where n is the number of unpaired electrons in the d-orbital of the metal ion Mⁿ⁺. For example, Fe³⁺ (3d⁵) has n = 5, so μ = √35 = 5.92 BM.

Ans. Lanthanoid contraction is the steady decrease in atomic and ionic radii of the 4f-block elements from La to Lu (a total drop of about 17 pm). It arises because 4f electrons shield the nuclear charge poorly. The consequence is that 4d and 5d transition elements of the same group (e.g. Zr and Hf, Nb and Ta) have nearly identical sizes and similar chemistry.

Ans. Cr is [Ar]3d⁵4s¹ and Cu is [Ar]3d¹⁰4s¹. A half-filled (d⁵) or fully filled (d¹⁰) d-subshell is extra-stable due to exchange energy and symmetric distribution of electrons. The 4s electron promotes to 3d to achieve this stable configuration.

Ans. KMnO₄ changes its n-factor with the medium: 5 in acidic solution (Mn⁷⁺ to Mn²⁺), 3 in neutral or faintly alkaline solution (Mn⁷⁺ to Mn⁴⁺, forming MnO₂), and 1 in strongly alkaline solution (Mn⁷⁺ to Mn⁶⁺, forming MnO₄^2-). Always check the medium before solving a redox titration.

Ans. Transition metals have (n-1)d and ns electrons of comparable energy, so both shells can lose electrons. Mn shows the widest range (+2 to +7) because its 3d⁵4s² configuration provides seven outer electrons that can all participate in bonding.

Ans. Mn shows oxidation states +2, +3, +4, +6 and +7 in standard compounds. Mn(+2) is the most stable in aqueous solution because losing the two 4s electrons gives 3d⁵ high-spin half-filled configuration with maximum exchange energy. Mn(+7) is the highest oxidation state in the 3d series and is realised in KMnO₄.

Ans. The lanthanoid contraction consequences are: (i) nearly identical sizes of 4d and 5d transition metals of the same group, so Zr/Hf and Nb/Ta are chemically inseparable; (ii) decreasing basicity of trivalent hydroxides from La(OH)₃ to Lu(OH)₃; (iii) closely spaced ionisation enthalpies that make individual lanthanoid separation industrially difficult.

Ans. The equilibrium 2CrO₄^2- + 2H⁺ Cr₂O₇^2- + H₂O is pH-controlled. Adding acid shifts it right, giving the orange Cr₂O₇^2- ion in dichromate solutions. Adding base shifts it left, giving the yellow CrO₄^2- ion in chromate solutions.

Ans. Most transition metal compounds are coloured because of d-d electronic transitions in the crystal field, where an electron absorbs a part of the visible spectrum and jumps from one d-orbital to another of higher energy. Sc³⁺, Ti⁴⁺ (d⁰) and Cu⁺, Zn²⁺ (d¹⁰) lack a possible d-d transition and are colourless.

Ans. Transition metals are good catalysts because they have variable oxidation states (allowing electron exchange in a reaction cycle) and partially filled d-orbitals (providing adsorption sites). V₂O₅ catalyses the Contact process, Fe catalyses the Haber process, Ni catalyses hydrogenation, and Pt catalyses catalytic converters.

Ans. Interstitial compounds are non-stoichiometric solids formed when small atoms (H, C, N, B) occupy lattice voids of transition metals, giving hard, high-melting, chemically inert materials like TiC and Mn₄N. Alloy formation is favoured by the similar atomic radii of transition metals. Brass (Cu-Zn), bronze (Cu-Sn), stainless steel (Fe-Cr-Ni) and misch metal (95% Ln + 5% Fe) are textbook alloys.

Ans. Lanthanoids have the configuration [Xe] 4f^1-14 5d^0-1 6s² and are predominantly +3 with a few +2/+4 exceptions. Actinoids have [Rn] 5f^1-14 6d^0-1 7s² and show oxidation states up to +7 (Np, Pu). All actinoids are radioactive; actinoid contraction is larger per element than lanthanoid contraction because 5f electrons shield even less effectively than 4f.