Chemistry
25 flashcards
~13 min
Transition Metals and Coordination Compounds
Explore the rich and colourful chemistry of transition metals with this comprehensive inorganic chemistry flashcard deck. Transition metals are among the most important elements in chemistry, biology, and industry — from the iron in your blood to the titanium...
About this deck
Explore the rich and colourful chemistry of transition metals with this comprehensive inorganic chemistry flashcard deck. Transition metals are among the most important elements in chemistry, biology, and industry — from the iron in your blood to the titanium in aircraft to the platinum in catalytic converters. This deck covers the general properties of d-block transition metals, variable oxidation states, colour of transition metal ions and the d-d transition, catalytic properties, magnetic properties, complex ion formation, ligands, coordination numbers, naming coordination compounds (IUPAC), stability constants, and biologically important transition metal complexes including haemoglobin and chlorophyll. Essential for A-Level Chemistry and university inorganic chemistry.
Ready to test yourself?
Flip through all 25 cards in interactive study mode.
All flashcards
Click any question to reveal the answer.
An element that forms at least one stable ion with a partially filled d subshell. Note: Zinc (Zn) and Scandium (Sc) are d-block elements but not transition metals by this strict definition (Zn²⁺ has full d¹⁰; Sc³⁺ has empty d⁰).
1. Variable oxidation states. 2. Form coloured ions. 3. Act as catalysts. 4. Form complex ions with ligands. Also: high melting/boiling points, good conductors, high density.
Their 3d and 4s electrons have similar energies — different numbers can be involved in bonding. Example: Iron: Fe²⁺ (3d⁶4s⁰) and Fe³⁺ (3d⁵4s⁰). Manganese shows the most: +2 to +7.
They absorb specific wavelengths of visible light to promote electrons between d orbitals of different energy levels (d-d transitions) — when the d subshell is partially filled. The transmitted/reflected colour is complementary to the absorbed colour.
Cu⁺ has the electron configuration [Ar]3d¹⁰ — a full d subshell. No d-d transitions are possible → no visible light absorbed → colourless. (Cu²⁺ with 3d⁹ is blue/green because d-d transitions are possible.)
A central metal ion surrounded by ligands (molecules or ions that donate lone pairs). Written in square brackets: [Fe(H₂O)₆]³⁺. The charge = metal oxidation state + sum of ligand charges.
An ion or molecule that donates a lone pair of electrons to a central metal ion, forming a coordinate (dative covalent) bond. Examples: H₂O, NH₃, Cl⁻, CN⁻, OH⁻, ethylenediamine (en).
A ligand that forms one coordinate bond to the central metal ion. Examples: H₂O, NH₃, Cl⁻, CN⁻, CO.
A ligand that forms two coordinate bonds to the central metal ion simultaneously. Examples: ethylenediamine (en, H₂N-CH₂-CH₂-NH₂), oxalate (C₂O₄²⁻), 2,2-bipyridine.
A ligand that forms three or more coordinate bonds. Most famous example: EDTA⁴⁻ (ethylenediaminetetraacetate) — a hexadentate ligand that wraps around a metal ion at 6 points. Used in chelation therapy and as a preservative.
Polydentate ligands form more stable complexes than equivalent monodentate ligands. Entropy-driven: replacing several monodentate ligands with one polydentate ligand increases the number of particles → increases entropy (ΔS > 0) → more negative ΔG.
The number of coordinate bonds formed between the central metal ion and its ligands. Most common: 6 (octahedral) and 4 (tetrahedral or square planar). Example: [Fe(H₂O)₆]³⁺ has coordination number 6.
Octahedral (6 ligands): Most common, e.g., [Fe(H₂O)₆]³⁺. Tetrahedral (4 ligands): e.g., [CoCl₄]²⁻. Square planar (4 ligands): Common with Pt²⁺, Pd²⁺, Au³⁺, e.g., cisplatin [Pt(NH₃)₂Cl₂].
Order: (1) Ligands alphabetically (with prefixes di, tri, tetra for count). (2) Metal name (Latin for anion complexes: ferrate, cuprate). (3) Oxidation state in Roman numerals. Example: [Fe(H₂O)₆]³⁺ = hexaaquairon(III).
The equilibrium constant for the formation of a complex ion. Larger Kstab = more stable complex. Example: [Fe(CN)₆]⁴⁻ has a very large Kstab → very stable → CN⁻ binds tightly to Fe²⁺.
A protein in red blood cells that carries oxygen. Contains iron (Fe²⁺) in a haem group — a porphyrin ring complex. O₂ binds reversibly to Fe²⁺. CO binds irreversibly (~200× more strongly than O₂) → carbon monoxide poisoning.
The green pigment in plants responsible for photosynthesis. Contains magnesium (Mg²⁺) at the centre of a porphyrin ring. Absorbs red and blue light; reflects green light (hence plants appear green).
cis-[Pt(NH₃)₂Cl₂] — a square planar platinum complex used as a chemotherapy drug. The cis arrangement allows it to cross-link DNA strands in cancer cells, preventing replication. The trans isomer is inactive.
The d-block spans groups 3–12 of the periodic table (periods 4–7), where d orbitals are being filled. Period 4 d-block: Sc, Ti, V, Cr, Mo, Mn, Fe, Co, Ni, Cu, Zn — 10 elements per period, 40 d-block elements total.
Cr: [Ar]3d⁵4s¹ (not [Ar]3d⁴4s²) — half-filled d shell is extra stable. Cu: [Ar]3d¹⁰4s¹ (not [Ar]3d⁹4s²) — fully filled d shell is extra stable. These are exceptions to the Aufbau principle.
A reaction where one ligand in a complex ion is replaced by another. Example: [Cu(H₂O)₆]²⁺ + 4NH₃ → [Cu(NH₃)₄(H₂O)₂]²⁺ + 4H₂O. Colour changes from pale blue (water complex) to deep blue (ammonia complex).
[Cu(H₂O)₆]²⁺ (pale blue) + 2OH⁻ → [Cu(OH)₂(H₂O)₄] (pale blue/green precipitate). The precipitate is copper(II) hydroxide. It does NOT dissolve in excess NaOH. (Contrast with Al³⁺ which dissolves in excess NaOH.)
First forms Cu(OH)₂ precipitate, then the precipitate dissolves in excess NH₃: Cu(OH)₂ + 4NH₃ → [Cu(NH₃)₄(H₂O)₂]²⁺ — a deep, intense blue solution. This is the tetraamminecopper(II) complex.
A list of ligands ranked by their ability to split d-orbital energy levels (crystal field splitting Δ). Strong-field ligands (CN⁻, CO) cause large splitting → absorb high-energy light (appear yellow/red). Weak-field ligands (Cl⁻, H₂O) cause small splitting → absorb low-energy light (appear blue/green).
Fe: Haber Process (NH₃ synthesis). V₂O₅: Contact Process (H₂SO₄ production). Pt/Pd/Rh: Catalytic converters (car exhaust). Ni: Hydrogenation of vegetable oils (margarine). MnO₂: Decomposition of H₂O₂. Their variable oxidation states allow them to form intermediates and regenerate.