D- And F- Block Elements Revision Notes for Chemistry NEET

The d-block and f-block elements are important sections in the periodic table, studied under Transition Elements and Inner Transition Elements. The d-block elements, known as transition elements, are those where the last electron enters the d-orbital. They mainly include elements from Group 3 to 12. The f-block elements, positioned separately at the bottom of the table, are called inner transition metals and consist of lanthanoids and actinoids. Understanding their general properties, electronic configurations, and characteristic behaviours is crucial for NEET Chemistry.

General Introduction and Electronic Configuration of Transition Elements Transition elements are characterized by the partial filling of d-orbitals in their atoms or ions. The general electronic configuration for d-block elements is $(n-1)d^{1-10}ns^{1-2}$. For example, Scandium ($Sc$) has the configuration $[Ar]\ 3d^1 4s^2$, while Zinc ($Zn$) ends with $3d^{10} 4s^2$. These elements display unique properties due to the presence of unpaired electrons and the relatively small difference in energy between the $ns$ and $(n-1)d$ subshells.

Occurrence and Characteristics Transition metals are commonly found as ores in the Earth’s crust. For instance, Iron is extracted from haematite ($Fe_2O_3$), while Copper is found in chalcopyrite ($CuFeS_2$). These metals are usually hard, possess high melting and boiling points, and are good conductors of heat and electricity. An important feature is their ability to show variable oxidation states.

• All transition elements are metals with high density and atomic/ionic sizes smaller than their s-block counterparts.
• They commonly form coloured compounds and are often good catalysts.
• Variable oxidation states arise due to the close energy levels of $ns$ and $(n-1)d$ electrons.

General Trends in Properties of First-Row Transition Elements ($3d$-Series) The first-row transition elements range from Scandium to Zinc. They show many periodic trends and exceptions that are frequently tested in NEET.

Physical Properties

• High melting and boiling points (except Zn, Cd, Hg due to fully filled d-orbitals).
• Metals are hard, strong, and ductile.
• Good thermal and electrical conductivity.

Ionization Enthalpy Ionization enthalpy gradually increases across the series with minor irregularities due to extra stability of half-filled ($d^5$) and fully filled ($d^{10}$) subshells. Transition elements have higher values than s-block but less than p-block elements.

Oxidation States The transition metals exhibit variable oxidation states, usually differing by one unit. For instance, Iron can exist as $Fe^{2+}$ and $Fe^{3+}$ ions; Manganese shows oxidation states from +2 up to +7. This variation is due to the participation of both $ns$ and $(n-1)d$ electrons in bonding.

Atomic Radii Across the period, atomic radii of d-block elements decrease at first due to increased nuclear charge, but tend to remain almost constant in the middle of the series, a phenomenon called lanthanoid contraction.

Colour, Catalytic Behaviour, and Magnetic Properties Most transition metal compounds are coloured due to d–d electronic transitions. They often serve as catalysts in industrial reactions (e.g., $V_2O_5$ in the Contact Process). Transition metals are usually paramagnetic because of unpaired d-electrons. The magnetic moment is given by $μ = \sqrt{n(n+2)}$ Bohr Magneton (B.M.), where $n$ is the number of unpaired electrons.

Complex Formation and Interstitial Compounds Transition metals easily form complexes, due to their small size and high charge/radius ratio. They can also trap smaller atoms like H, C, or N in the crystal lattice, forming interstitial compounds.

Alloy Formation Transition metals easily form a wide range of alloys such as steel (Fe–C), bronze (Cu–Sn), and brass (Cu–Zn) due to similar atomic sizes. Their alloys are harder and more resistant to corrosion than pure metals.

Preparation, Properties, and Uses of Potassium Dichromate ($K_2Cr_2O_7$) and Potassium Permanganate ($KMnO_4$)

• Potassium Dichromate ($K_2Cr_2O_7$): Prepared from chromite ore ($FeCr_2O_4$) through roasting and chemical processes. It is a strong oxidising agent, used in volumetric analysis, dyes, and tanning leather.
• Potassium Permanganate ($KMnO_4$): Prepared by alkaline oxidation of manganese dioxide ($MnO_2$). It acts as a powerful oxidising agent in acidic, neutral, and alkaline media. It is used in water treatment, medicine, and as a titrant in redox titrations.

Inner Transition Elements: Lanthanoids and Actinoids Inner transition elements are the f-block elements, split as Lanthanoids ($Ce$ to $Lu$) and Actinoids ($Th$ to $Lr$). Their differentiating electron enters the $4f$ or $5f$ orbitals respectively.

Lanthanoids

• Their general electronic configuration is $[Xe]\ 4f^{1-14}\ 5d^{0-1}6s^2$.
• The most common oxidation state is +3, but +2 and +4 are also possible for a few elements.
• Lanthanoid contraction refers to the gradual decrease in ionic and atomic radii with increasing atomic number.

Actinoids Actinoids exhibit a wide range in oxidation states, often between +3 to +7. Their general electronic configuration is $[Rn]\ 5f^{1-14}\ 6d^{0-1}\ 7s^2$. Most actinoids are radioactive. Examples include Uranium ($U$), Thorium ($Th$), and Plutonium ($Pu$). The chemistry of actinoids is complex due to variable oxidation states and radioactive nature.

Summary Table: Key Features of D- and F-Block Elements

Feature	Transition Elements (d-block)	Inner Transition Elements (f-block)
Electronic Configuration	$(n-1)d^{1-10}ns^{1-2}$	Lanthanoids: $4f^{1-14}$, Actinoids: $5f^{1-14}$
Common Oxidation State	Variable (+2, +3, ... up to +7)	+3 most common
Complex Formation	Strong tendency	Lanthanoids: moderate; Actinoids: higher
Magnetism	Paramagnetic	Highly paramagnetic
Examples	Fe, Cu, Mn, Cr	Ce, U, Th, Pu

Conclusion The d- and f-block elements showcase a remarkable array of chemical and physical properties that make them essential for real-world applications and conceptual questions in NEET Chemistry. Their study involves understanding trends in the periodic table, properties, structure of compounds, and the nature of chemical bonding. Effective revision of their characteristics, trends, and special compounds can provide a scoring advantage in NEET.

NEET Chemistry Notes – D- And F- Block Elements: Essential Revision Points

These revision notes for NEET Chemistry: D- and F- Block Elements help you recap vital trends such as variable oxidation states and complexation. You can understand general properties, electronic configurations, and practical uses quickly. These concise notes provide clarity on both transition elements and inner transition elements for last-minute preparation.

With easy-to-read formats, tables, and lists, these notes strengthen your grasp of key exam facts. Students can review important compounds like K2Cr2O7 and KMnO4 and visualize periodic trends for confident answers on test day. Focused learning makes mastering this chapter faster and more effective.