3.4 D Block

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Page 2: D-Block Transition Metals

• Definition of Transition Metals

  • Metals with a partially filled d-subshell as an atom or in its stable ion.

  • Zinc is classified as a transition metal despite having a fully filled d-subshell.

• Electron Configuration

  • General electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴ .

  • Argon (Ar) is used as a reference for noble gas configurations.

• Subshell Filling

  • 4s subshell is filled before the 3d subshell.

  • The 4s subshell loses electrons first during oxidation, except for exceptions like Copper (Cu) and Chromium (Cr).

• Examples of Common Ions

  • Common ions such as Fe²⁺ and Mn⁷⁺ are formed by losing electrons from the 4s and 3d subshells.

• Transition Metals Characteristics

  • Can form colored compounds and complexes.

  • Involved in redox reactions, function as catalysts.

• Ligands

  • A ligand is a small molecule with a lone pair of electrons that can form coordinate bonds with transition metals.

  • Ligands provide electron pairs for bonding, forming complex ions.

Page 3: Complex Formation

• Ligand Arrangement

  • Ligands around a central transition metal create specific geometrical shapes: octahedral and tetrahedral.

• Examples of Complexes

  • [Fe(H₂O)₆]³⁺: Pale green complex (octahedral).

  • [Cu(NH₃)₄(H₂O)₂]²⁺: Royal blue complex (octahedral).

  • [CuCl₂]²⁻: Blue complex (tetrahedral).

  • [Cu(NH₃)₄(H₂O)₂]²⁺ and [CuCl₂]²⁻ exhibit different conformations: cis and trans isomers.

• Le Chatelier's Principle

  • If more reactants are added, equilibrium shifts to the right, increasing the concentration of products.

  • The addition of ligands can change the color of the complex, indicative of shifts in equilibrium.

Page 4: Color and Properties of Complexes

• Color Formation

  • Some complexes are colorless due to fully filled d-orbitals with no empty spaces for electron promotion.

• Orbital Splitting

  • 3d subshell splits when ligands approach, creating higher and lower energy levels.

  • Electrons can be excited from lower to higher energy levels, absorbing specific light frequencies and reflecting complementary colors.

• Transition Metals as Catalysts

  • Catalysts increase reaction rate by providing a lower energy pathway (

  • Example: Iron in the Haber process is a heterogeneous catalyst.

  • Variable oxidation states of transition metals allow for participation in various reactions and redox chemistry.

Page 5: Hydroxide Reactions with Transition Metals

• Reactions with Hydroxide Ions

  • Transition metals with high positive charge density often behave as acids, donating protons (H⁺).

  • Example reactions: Formation of hydroxide complexes.

• Amphoteric Properties

  • Certain transition metal complexes can act as both acids and bases (amphoteric).

  • Specific reactions: [Cr(H₂O)₆]³⁺ reacting with OH⁻ to form colored precipitates.

• Color Indicators in Reactions

  • A pale blue precipitate indicates [Cu(H₂O)₄(OH)₂] formation.

  • If precipitates dissolve upon the addition of excess NaOH, the metal is confirmed as amphoteric.