Grade 12
  1. Solid state  1.1. Classification of solids  1.2. Crystal Lattice and Unit Cell  1.3. Packing Efficiency  1.4. Density of unit cell  1.5. Imperfections in solids (point and line defects)  1.6. Electrical Properties of Solids (Conductors, Insulators and Semiconductors)  1.7. Magnetic Properties of Solids (Diamagnetic, Paramagnetic and Ferromagnetic Materials)
  2. Solution  2.1. Types of Solutions (Homogeneous and Heterogeneous)  2.2. Expressing concentration of solutions (mass %, volume %, molarity, molality, normality, mole fraction)  2.3. Solubility of solids and gases in liquids (Henry's law)  2.4. Raoult's Law and Ideal and Non-Ideal Solutions  2.5. Syndrome properties  2.6. Abnormal molar mass and Van't Hoff factor
  3. Electrochemistry  3.1. Electrochemical cells (galvanic and electrolytic cells)  3.2. Galvanic cell and EMF of the cell  3.3. Standard electrode potential and electrochemical series  3.4. Nernst equation and its applications  3.5. Conductivity and electrolytic cells (specific, molar and equivalent conductivity)  3.6. Kohlrausch's law and its applications  3.7. Batteries (primary and secondary cells)  3.8. Corrosion and its prevention
  4. Chemical kinetics  4.1. Rate of chemical reaction  4.2. Factors affecting the reaction rate (concentration, temperature, catalyst, surface area)  4.3. Order and molecularity of the reaction  4.4. Integrated Rate Equations (Zero, First and Second Order)  4.5. Half-life of a reaction  4.6. Collision theory and activation energy  4.7. Arrhenius equation and its applications
  5. Surface chemistry  5.1. Adsorption and its types (Physicosorption and Chemisorption)  5.2. Catalysis and its types (homogeneous and heterogeneous)  5.3. Colloids and their properties (Tyndall effect, Brownian motion, coagulation)  5.4. Emulsions and gels  5.5. Applications of Colloids
  6. General principles and processes of separation of elements  6.1. Presence of metals and minerals  6.2. Concentration of ores (gravity separation, froth flotation, magnetic separation)  6.3. Extraction of raw metals (roasting, calcination, reduction)  6.4. Thermodynamic and electrochemical principles of metallurgy  6.5. Refining of metals
  7. P-block elements  7.1. Group 15 elements (nitrogen and phosphorus)  7.2. Group 16 Elements (Oxygen, Sulphur and their Compounds)  7.3. Group 17 Elements (Halogens and their Compounds)  7.4. Group 18 Elements  7.5. Properties and Trends in p-Block Elements  7.6. Important compounds of p-block elements (ammonia, phosphine, sulphuric acid, hydrochloric acid)  7.7. Interhalogen compounds and their applications
  8. d-block and f-block elements  8.1. General Properties of Transition Metals  8.2. Properties of Inner Transition Metals (Lanthanoids and Actinoids)  8.3. Lanthanoid and actinoid contractions  8.4. Coordination Chemistry of d-Block Elements
  9. Coordination compounds  9.1. Werner's theory and modern concepts  9.2. Coordination number and type of ligand  9.3. Nomenclature of Coordination Compounds  9.4. Isomerism (geometrical and optical) in coordination compounds  9.5. Bonding in Coordination Compounds (Valence Bond Theory and Crystal Field Theory)  9.6. Stability and applications of coordination compounds in medicine and industry
  10. Haloalkanes and haloarenes  10.1. Classification and nomenclature of haloalkanes and haloarenes  10.2. Physical and Chemical Properties of Haloalkanes and Haloarenes  10.3. Mechanism of Nucleophilic Substitution Reactions (SN1 and SN2)  10.4. Uses and environmental effects (ozone depletion, CFCs)
  11. Alcohol, phenol and ether  11.1. Structure and classification of alcohols, phenols and ethers  11.2. Preparation and properties of alcohols  11.3. Preparation and properties of phenol  11.4. Preparation and properties of ethers  11.5. Chemical Reactions and Uses
  12. Aldehydes, ketones and carboxylic acids  12.1. Structure and nomenclature in aldehydes, ketones and carboxylic acids  12.2. Preparation and properties of aldehydes and ketones  12.3. Chemical reactions in aldehydes, ketones and carboxylic acids (nucleophilic addition, oxidation and reduction)  12.4. Preparation and Properties of Carboxylic Acids  12.5. Chemical Reactions and Uses of Carboxylic Acids
  13. Nitrogen-containing organic compounds  13.1. Amines (classification, structure, basicity)  13.2. Preparation and properties of amines  13.3. Reactions of Amines (Diazotization, Carbylamine Reaction)  13.4. Diazonium salts and their applications in paint industry
  14.1. Carbohydrates (classification and properties)  14.2. Proteins (Structure and Function)  14.3. Enzymes (Mechanism and Function)  14.4. Nucleic acids (DNA and RNA)  14.5. Vitamins and hormones
  15. Polymer  15.1. Classification of Polymers (Addition, Condensation, Copolymers)  15.2. Types of polymerization (free radical, ionic, condensation)  15.3. Important Polymers and Their Uses  15.4. Biodegradable and non-biodegradable polymers
  16. Chemistry in Everyday Life  16.1. Drugs and their classification (analgesics, antipyretics, antibiotics, antacids)  16.2. Chemicals in food and cosmetics (preservatives, artificial sweeteners, antioxidants)  16.3. Cleaning agents and detergents (soaps, synthetic detergents, surfactants)  16.4. Environmental Chemistry (Pollution, Green Chemistry, Sustainable Chemistry)

Grade 12 → d-block and f-block elements ↓


Coordination Chemistry of d-Block Elements


Coordination chemistry is an important topic when it comes to the chemistry of d-block elements. It explores how transition metals form complexes with ligands, which are molecules or ions that can donate a pair of electrons to the metal. The field of coordination chemistry is central to many processes in nature and technology, including catalysis, materials science, and bioorganic chemistry.

Introduction to d-block elements

The d-block elements, also called transition metals, are found in the middle part of the periodic table, spanning from groups 3 to 12. These elements are characterized by having a partially filled d-subshell in their atomic or ionic forms. Their notable properties include the ability to form different oxidation states, exhibit a wide range of colors in their compounds, and form complex ions with ligands.

Ligands: Coordination partners

Ligands are atoms, ions, or molecules that can donate at least one pair of electrons to the central metal atom or ion in a coordination complex. They can be classified based on their denticity, which indicates the number of donor sites they have. Generally, ligands are classified as:

  • Monodentate ligands: These ligands have only one donor site. Examples include NH3 (ammonia), H2O (water), and Cl- (chloride ion).
  • Bidentate ligands: These ligands have two donor sites. Examples include ethylenediamine (en) and oxalate ion (C2O42-).
  • Polydentate ligands: These ligands have more than two donor sites. An example is EDTA4- (ethylenediaminetetraacetate), which can bind to a metal at six coordination sites.

Complex and coordination numbers

Coordination compounds contain a central metal atom or ion bound to a group of ligands. The coordination number of a metal in a compound refers to the total number of coordination bonds formed between the central metal and the ligands. Some common coordination numbers include:

  • Coordination number 4: Complexes often have tetrahedral or square planar geometry. An example of a square planar complex is [PtCl4]2-
  • Coordination number 6: The most common geometry for coordination number six is octahedral. An example of this is [Co(NH3)6]3+

Other coordination numbers may also occur, but they are less common in transition metal complexes.

Electronic configuration and bonding in coordination compounds

The d-block elements have unique electronic configurations due to the involvement of d-orbitals, which significantly affect their chemical behaviour and bonding characteristics. The electronic configuration of these elements can generally be expressed as:

 [noble gas] (n-1)dx nsy

Where x represents the number of electrons in the d-orbital and y represents the number of electrons in the s-orbital. Coordination compounds are formed when the metal ion accepts electron pairs from the ligand into its d-orbital.

Crystal field theory (CFT)

Crystal field theory (CFT) is a model that describes the electronic structure of transition metal complexes. It focuses on the effect of electrostatic interactions between electrons from the metal ion and the ligand. The presence of the ligand affects the energy levels of the d-orbitals, splitting them into different energy states.

In an octahedral compound, the five d-orbitals are split into two sets: t2g orbitals (low energy) and eg orbitals (high energy). This splitting can be represented as:

 E | --- eg | --- t2g |

The extent of the splitting depends on several factors, including the nature of the metal ion and the type of ligand involved. Strong field ligands, such as CN- and CO, cause large splitting of the d-orbitals, whereas weak field ligands, such as H2O, cause small splitting.

Colour of transition metal complexes

The color of transition metal complexes is due to d-d electronic transitions, which occur when electrons are promoted from lower energy d-orbitals to higher energy d-orbitals within split d-levels. The energy difference between these orbitals is analogous to the energy of visible light, which is absorbed when the transition occurs.

For example, the complex [Ti(H2O)6]3+ appears purple because it absorbs yellow light, which is opposite to violet on the color wheel. The specific color observed depends on the metal, its oxidation state, the ligands present, and the crystal field splitting.

Examples of coordination complexes

1. [Fe(CN)6]4- complex

This complex is known as the hexacyanoferrate(II) ion. It is a coordination complex consisting of a central iron (Fe2+) ion surrounded by six cyanide ligands. Cyanide ions, being strong field ligands, cause significant crystal field splitting, resulting in a low spin configuration for the d-orbitals.

2. [Cu(NH3)4]2+ complex

In the tetraamminecopper(II) complex, copper is surrounded by four ammonia ligands. It exhibits a distorted square planar geometry due to the Jahn-Teller effect, which is common in such d9 complexes.

3. [Co(en)3]3+ complex

Tris(ethylenediamine)cobalt(III) complex contains three ethylenediamine ligands, which are bidentate in nature. They surround the cobalt ion in octahedral geometry. This complex is chiral and can exist as two enantiomers.

Biological importance of coordination compounds

Coordination compounds play important roles in biological systems. Here are some important examples:

  • Hemoglobin: The oxygen-transporting protein in red blood cells is a coordination compound containing a central metal iron. It binds oxygen molecules, which are then transported to tissues throughout the body.
  • Vitamin B12: An essential nutrient for humans that contains a cobalt-centered coordination complex. It plays a vital role in brain function and the production of DNA.
  • Chlorophyll: The green pigment found in plants that is important for photosynthesis. It has magnesium at its core and helps plants capture the energy of sunlight.

Applications of coordination compounds

In addition to their biological importance, coordination compounds have a wide range of applications in industry and technology:

  • Catalysts: Many catalytic processes in the chemical industry are mediated by coordination complexes. For example, Zeise's salt is a complex of platinum that plays an important role in catalyzing hydrogenation reactions.
  • Chemotherapy: Cisplatin is a coordination compound of platinum that is widely used in the treatment of cancer due to its ability to interfere with DNA replication in cancer cells.
  • Analytical chemistry: Coordination compounds such as EDTA are commonly used as complexing agents in titration procedures to determine the concentration of metal ions in solution.

Conclusion

Coordination chemistry of d-block elements is a remarkable field that sheds light on the complexities of metal-ligand interactions and their diverse implications in the natural world as well as human technology. Understanding the fundamentals of coordination complexes, such as ligand type, coordination number and electronic structure, provides valuable insights into their functioning and applications.


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Coordination Chemistry of d-Block Elements

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