Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Inorganic chemistry → Main Group Chemistry ↓


Transition metals and their complexes


Transition metals, although part of the larger field of inorganic chemistry, hold a special place because of their unique properties and wide range of applications. These metals are found in the d-block of the periodic table and are known for their ability to form complex compounds, vibrant colors, and variable oxidation states. The purpose of this lesson is to explore the fascinating world of transition metals and their complexes, including examples and illustrations to aid understanding.

Introduction to transition metals

Transition metals are elements found in groups 3 to 12 of the periodic table, including iron, copper, nickel, chromium, and other elements. These metals are characterized by the presence of an incomplete d-subshell in one or more of their oxidation states. Some of the key characteristics of transition metals include:

  • Variable oxidation states: Transition metals can exhibit a number of oxidation states, allowing them to participate in a wide range of chemical reactions.
  • Formation of complexes: They can form complex ions by binding with various ligands.
  • Coloured compounds: Due to d-d electron transition, these metals often form coloured compounds.
  • Magnetic properties: Many transition metals show magnetic properties due to the presence of unpaired d electrons.

Characteristics of transition metals

Below is a brief overview of some of the defining characteristics:

Variable oxidation states

Transition metals can lose different numbers of electrons, allowing them to switch between different oxidation states. For example, iron can exist as Fe 2+ and Fe 3+ ions.

Fe ⇒ Fe 2+ + 2e - Fe ⇒ Fe 3+ + 3e -

Creation of complexes

Transition metals have a tendency to form coordination complexes with ligands. A ligand is a molecule or ion that can donate a pair of electrons to the metal. Some common ligands include water, ammonia, and chloride ions. For example, copper can form a complex with ammonia:

[Cu(NH 3) 4 ] 2+

Colored compounds

One of the most distinctive features of transition metal complexes is their color. The colors arise from electronic transitions of d electrons between different energy levels. For example, [Cu(NH 3) 4 ] 2+ complex is dark blue.

Cu(NH 3) 4

Magnetism

The magnetic properties in transition metals are due to the presence of unpaired electrons. For example, iron, cobalt and nickel are known for their ferromagnetic properties. The unpaired d electrons align themselves in the presence of a magnetic field.

Transition metal complexes

Transition metal complexes contain a central metal ion bound to a group of surrounding ligands. These complexes show a wide variety of geometric arrangements and exhibit characteristic properties.

General geometry

  • Octahedral: Six ligands symmetrically arranged around a central atom, with a coordination number of six in general. Example: [Fe(CN) 6] 4-.
  • Tetrahedral: Four ligands arranged in a tetrahedral shape, with coordination number four in common. Example: [NiCl 4] 2-.
  • Square planar: Four ligands located at the corners of a square in the same plane. Example: [PtCl 4] 2-.

Let's imagine octahedral geometry:

l l l l

Ligand field theory

Ligand field theory explains the splitting of d-orbital energy in transition metal complexes. The presence of ligands changes the energy levels of d orbitals, causing their splitting. For octahedral complexes, the d orbitals split into two sets: t 2g and e g.

T2G e.g.

This splitting causes different absorption of light, resulting in the observed colours of the complexes.

Stability of complexes

The stability of a transition metal complex is affected by various factors such as the nature of the metal, the ligands and the overall geometry. Some of the important concepts are as follows:

  • Chelation: The formation of multiple bonds between a single ligand and the metal center increases the stability of the complex.
  • Crystal field stabilization energy (CFSE): Stabilization achieved by the distribution of electrons within split d orbitals.
  • Entropy/enthalpy change: Thermodynamic parameters that govern the formation and stability of complexes.

Applications of transition metals and complexes

Understanding the transition metals and their complexes has led to many applications in a variety of industries:

Catalysis

Transition metals are important in catalytic processes. They provide active sites for chemical reactions and are used in both homogeneous and heterogeneous catalysis. An example of this is the catalytic role of iron in the Haber process for ammonia synthesis.

Biological significance

Many biological processes depend on transition metal complexes. Hemoglobin, a complex of iron, is important for oxygen transport in the blood. Other examples include chlorophyll (magnesium complex) and vitamin B12 (cobalt complex).

Physics

Transition metals are essential for the development of new materials with unique properties, such as superconductors, magnets, and alloys.

Medical applications

Transition metal complexes are used in medical diagnosis and treatment. Cisplatin, a platinum complex, is widely used in cancer therapy.

Conclusion

Transition metals and their complexes play important roles in both chemistry and everyday life. From colorful compounds to important biological processes, the versatility of these metals continues to inspire both research and industry. Understanding their properties and behaviors provides valuable insights into the fundamental workings of chemistry and its applications. Through this lesson, we explored the properties, behaviors, and diverse roles of transition metals and their complexes.


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Transition metals and their complexes

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