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Transition Metals and Coordination Compounds - General Chemistry

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  • What causes the color in transition metal compounds like Cr3+, Fe2+, and Cu2+?
    The color arises from electronic transitions between split d orbitals in the metal ion caused by ligand field effects.
  • How do transition metals form ions in terms of electron loss?
    Transition metals lose their ns electrons first, then the (n-1)d electrons when forming ions.
  • Describe the trend in atomic radii across the first three transition metal rows.
    Atomic radii are very similar across transition metals, with a small increase down a column and a small increase from the 1st to 2nd row; the 3rd row is about the same size as the 2nd due to lanthanide contraction.
  • How does first ionization energy change across the transition metal series?
    First ionization energy generally increases across the row but less sharply than in main group elements; the 3rd row has higher ionization energies than the 1st and 2nd rows.
  • What is the general trend of electronegativity in transition metals?
    Electronegativity generally increases across a row and from the 1st to 2nd row, with little difference between the 2nd and 3rd rows.
  • What is a coordination compound?
    A coordination compound is a neutral compound formed by a complex ion and its counterions.
  • Define ligand and metal ion in coordination chemistry.
    A ligand is a Lewis base that donates an electron pair; a metal ion is a Lewis acid that accepts electron pairs.
  • What is a coordinate covalent bond in coordination compounds?
    It is the bond formed between a ligand and a metal ion where the ligand donates both electrons.
  • What are monodentate, bidentate, and polydentate ligands?
    Monodentate ligands donate one electron pair; bidentate ligands donate two electron pairs from different atoms; polydentate ligands donate more than two electron pairs.
  • What is a chelate in coordination chemistry?
    A chelate is a complex ion containing bidentate or polydentate ligands; the ligand is called a chelating agent.
  • What is the typical range of coordination numbers in complexes?
    Coordination numbers typically range from 2 to 12, with odd numbers being rare.
  • How are coordination compounds named?
    Name the cation first, then the anion; ligands are named alphabetically with prefixes for quantity; metal oxidation state is given in Roman numerals; anionic complex metals end with '-ate'.
  • How are neutral and anionic ligands named in complexes?
    Neutral ligands use the molecule name (e.g., aqua for H2O, ammine for NH3); anionic ligands modify the ion name (e.g., -ide to -o, -ate to -ato).
  • What prefixes are used for multiple ligands in naming complexes?
    Use di-, tri-, tetra-, etc., unless the ligand name already has a prefix, then use bis-, tris-, tetrakis-, etc.
  • What are coordination isomers?
    Isomers where ligands and counterions exchange places between complex ions and counterions.
  • What are linkage isomers?
    Isomers where a ligand coordinates to the metal in different ways through different atoms.
  • Describe cis-trans isomerism in coordination compounds.
    Cis isomers have two identical ligands adjacent; trans isomers have them opposite each other.
  • What is fac-mer isomerism in octahedral complexes?
    Facial (fac) isomers have three identical ligands adjacent forming one face; meridional (mer) isomers have them arranged in an arc around the metal.
  • What are optical isomers in coordination chemistry?
    Non-superimposable mirror images of complexes that differ in how they rotate plane-polarized light.
  • What does Crystal Field Theory (CFT) explain in coordination compounds?
    CFT explains the splitting of metal d orbitals in complexes, accounting for color and magnetic properties.
  • What is crystal field splitting energy (Δ)?
    The energy difference between split d orbitals in a metal complex.
  • How does ligand type affect crystal field splitting energy?
    Strong field ligands cause large Δ; weak field ligands cause small Δ.
  • How does metal cation charge affect crystal field splitting energy?
    Higher metal cation charge increases Δ.
  • What is the difference between high-spin and low-spin complexes?
    High-spin complexes have small Δ and more unpaired electrons (paramagnetic); low-spin have large Δ, fewer unpaired electrons (diamagnetic).
  • How do tetrahedral and square planar complexes differ in magnetic properties?
    Tetrahedral complexes are usually high-spin and paramagnetic; square planar complexes are often low-spin and diamagnetic.
  • What are some applications of coordination compounds?
    Used in metal extraction, chemical analysis, coloring agents, biomolecules (e.g., hemoglobin), and drugs (e.g., cisplatin).
  • What role does EDTA play in coordination chemistry?
    EDTA is a hexadentate chelating agent used to bind metal ions, useful in heavy metal poisoning treatment.
  • What is the significance of porphyrins in biology?
    Porphyrins are coordination compounds that form the basis of hemoglobin and chlorophyll, essential for oxygen transport and photosynthesis.