Transition Metals Quiz

d-block Elements

• The d-block elements, groups 3-12, have progressively filling d orbitals in each long period of the periodic table.
• Transition metals are often used to refer to the d-block elements.
• Four series of transition metals exist: 3d (Sc to Zn), 4d (Y to Cd), 5d (La and Hf to Hg), and 6d (Ac and Rf to Cn).
• Two series of inner transition metals are lanthanoids (4f, Ce to Lu) and actinoids (5f, Th to Lr).
• Transition metals were originally defined as elements with transitional chemical properties between s and p-block elements.
• Transition metals, according to IUPAC, have incomplete d subshells in their neutral atoms or ions.
• Zinc, cadmium, and mercury (group 12) have full d¹⁰ configurations, and are not considered transition metals. However, their chemistry is studied alongside transition metals.

f-block Elements

• The f-block includes the lanthanoids and actinoids.
• Lanthanoids follow lanthanum, and actinoids follow actinium.
• Lanthanum is often included in discussions of lanthanoids.
• Actinoid chemistry is more complex due to a wider range of oxidation states and radioactivity.

Transition Metals (d-block): General Characteristics

• Physical properties: Most are hard, strong, ductile, malleable, good thermal and electrical conductors, with high melting/boiling points.
• The higher melting points are due to additional bonding involving (n-1)d electrons in addition to ns electrons.
• Melting points generally peak around d⁵ configuration, aside from Mn and Tc anomalies.
• Enthalpies of atomization are high, peaking mid-series due to unpaired electrons contributing to strong interatomic interaction (stronger bonding).
• Atomic/ionic sizes: Ionic radius generally decreases across a series due to increasing effective nuclear charge and imperfect shielding of d-electrons. Lanthanoid contraction occurs due to the incomplete shielding of 4f electrons, causing the atomic radii of the second/third series to be similar.
• Ionization Enthalpies: The first ionization enthalpy generally increases across a series, but the second and third ionization enthalpies show less steep increase, particularly at the middle of the series where half-filled d orbitals (like d⁵) have increased stability.
• Oxidation States: Transition metals exhibit a wide range of oxidation states (varying by 1, unlike non-transition elements, which vary by 2. The maximum oxidation state corresponds to the sum of s and d electrons in the uncharged form.
• Oxidation States (Trends): Elements in the middle of the series tend to exhibit the greatest range of oxidation states. Early in the series, the +2 state is common, but higher states stabilize, e.g., Ti⁴⁺, V⁵⁺, Cr⁶⁺. Late in the series, the +2 state is frequent.
• Electrode Potentials (M²⁺/M): General trend of less negative potentials across the series related to increasing ionization enthalpy variation. Mn, Ni, and Zn show irregularities due to exceptional stability of d⁵ and d¹⁰ configurations.
• Copper: Cu is unusual because its E₀(M²⁺/M) is positive, meaning it does not readily liberate H₂ from acids.
• Chemical Reactivity: Most elements except copper react with dilute mineral acids, although rates can be slow. Early elements are more reactive than later elements.

Formation and Properties of Complexes

• Transition metals form a variety of complex compounds due to small size, high charge, and available d orbitals.

Catalytic Activity

• Transition metals and their compounds demonstrate catalytic activity through multiple oxidation states and complex formation.

Interstitial Compounds

• Interstitial compounds are formed when small atoms (like H, C, or N) are trapped within the crystal lattice of a transition metal. They are chemically inert, and have high melting points and hardness.

Alloy Formation

• Alloys of transition metals are hard and often have high melting points due to similar radii and other characteristics. They're frequently used in steel production.

Lanthanoids (4f-block): General Characteristics

• Physical Properties: Silvery-white, rather soft metals, though hardness increases across the series. Good heat and electrical conductors.
• Atomic/ionic sizes: Exhibit lanthanoid contraction, leading to similar sizes of elements in the second and third transition series.
• Oxidation States: Mostly +3, but also +2 and +4 states depending on electronic configuration stability, and trends are similar to those of transition metals (depending on stability of electrons or d-orbitals).
• Coloration: Many trivalent ions exhibit coloration, probably due to 4f electron transitions.

Actinoids (5f-block): General Characteristics

• Physical Characteristics: Shiny, reactive metals with variable structures, reactivity, and similar irregularities due to differing radii and oxidation states.
• Oxidation states: Exhibit a wider range of oxidation states than lanthanoids, and +3 is mostly common, although higher states exist early in the series.
• Radioactivity: Many are radioactive, with varying half-lives, making their study challenging.

Applications of d- and f-block elements

• Wide ranging applications: steel production, catalysis, complexes, organic synthesis, pigments, batteries, coinage metals.