d and f

The d-Block Elements

  • The d-block elements are elements of groups 3-12 of the periodic table.

  • Properties:

    • d orbitals are progressively filled as atomic number increases.

    • Positioned in four long periods: 4, 5, 6, and 7.

    • Commonly referred to as transition elements due to their transitional properties between s and p-block elements.

  • Key series:

    • Four main series of transition metals based on their filling of d orbitals.

Transition Elements

  • Definition (IUPAC): Transition metals are defined as metals with incomplete d subshells in either their neutral atom or their ions.

  • Exceptions:

    • Zinc, Cadmium, and Mercury (group 12) have full d10 configuration, hence not considered transition metals, though their chemistry is often studied alongside.

  • Notable transition metals include:

    • Precious metals: Silver, Gold, Platinum.

    • Industrially important metals: Iron, Copper, Titanium.

Electronic Configurations of d-Block Elements

  • General configuration pattern: (n-1)d1-10 ns1-2.

  • (n-1) signifies inner d orbitals and ns denotes outermost orbitals.

  • Exceptions to expected configurations due to slight energy differences:

    • Chromium (Cr, Z=24): 3d5 4s1 instead of expected 3d4 4s2.

    • Copper (Cu, Z=29): 3d10 4s1 instead of the expected 3d9 4s2.

Physical Properties of Transition Elements

  • Display typical metallic properties, such as:

    • High tensile strength.

    • Ductility and malleability.

    • High thermal and electrical conductivity.

    • Metallic lustre.

  • Hardness: Generally hard with low volatility.

  • Melting and boiling points are high due to the involvement of d electrons in metallic bonding.

Trends in Melting Points

  • Melting points generally rise to maximum at d5 and fall regularly as atomic number increases, but have anomalies in certain metals (Mn and Tc).

  • Presence of unpaired d-electrons contributes to increased metallic strength.

  • Mn has a stable half-filled configuration, leading to tighter holding of electrons and reduced delocalisation, thus weaker metallic bonds.

Enthalpies of Atomization

  • Transition metals have high enthalpies of atomization, particularly favourable at mid-series due to unpaired electrons per d-orbital enhancing interatomic interactions.

  • Greater valence electron count generally correlates with stronger bonding.

Variation in Atomic and Ionic Sizes

  • Atomic radii tend to decrease across the 3d series with increasing atomic number due to poor shielding by d-orbitals.

  • Increase in effective nuclear charge decreases size while increased electron repulsion tends to increase size, leading to irregular variation.

  • Ionic radii also exhibit similar trends, although irregularities exist.

Atomic Radii of Transition Elements

  • Radius increases from the first (3d) series to second (4d) series.

  • Little change in third (5d) series radii, attributed to Lanthanoid contraction due to poor shielding by 4f electrons.

  • Zr and Hf exhibit similar radii, resulting in comparable properties.

Ionization Enthalpies

  • Generally, ionization enthalpy increases across the transition series due to increasing nuclear charge with the filling of d orbitals.

  • Notable trends:

    • Variability in ionization enthalpies is present; e.g., IE2: V < Cr > Mn, highlighting important configurations.

Oxidation States

  • Transition elements exhibit a wide variety of oxidation states, particularly those in the center of the series.

  • Oxidation state variability is influenced by incomplete d orbital filling and electron sharing capacity.

Stability in Aqueous Solutions

  • Stability of compounds in solution is reliant on electrode potentials rather than solely ionization enthalpies.

  • Electrode potential factors include enthalpy of sublimation, ionization enthalpy, and hydration enthalpy.

Trends in M2+/M and M3+/M2+ Standard Electrode Potentials

  • Typical patterns show less negative E values across the series.

  • Mn2+, Ni, and Zn exhibit unusually negative potentials due to d configuration stability influences.

  • High Eo for copper linked to sublimation and ionization enthalpies.

Formation and Properties of Coloured Ions

  • Transition metal ions are often coloured due to d-d electron transitions.

  • The absorbing frequency of light correlates with the complementary colours observed.

  • Factors influencing colour include nature and strength of ligands.

Formation of Complex Compounds

  • Transition metals readily form complex compounds due to their small ionic size, high ionic charge, and available d orbitals.

  • Example complexes include [Fe(CN)6]3– and [Cu(NH3)4]2+.

Alloy Formation and Catalytic Properties

  • Transition metals readily form alloys due to similar atomic radii and metallic characteristics.

  • Alloys such as stainless steel and brass confer hardness and high melting points.

  • Transition metals are effective catalysts due to variable oxidation states and complex formation.

Magnetic Properties and Conductivity

  • Two key types of magnetism:

    • Diamagnetism: Substances are repelled by magnetic fields.

    • Paramagnetism: Substances are attracted due to unpaired electrons, with ferromagnetism as a strong form of paramagnetism.

Transition Elements in Reactions and Oxidation

  • Transition elements demonstrate variable stability in different environments, such as oxidation reactions that differ based on their electronic configurations.

The f-Block Elements

  • The inner transition elements, where the last electron enters the (n-2)f orbitals, have unique properties compared to d-block elements.

  • Lanthanoids (4f series) and actinoids (5f series) display notable differences and similarities in chemical behaviour, oxidation states, and bonding characteristics.