The d- and f-Block Elements (Summary)

Vocabulary flashcards covering key terms and definitions from the lecture notes on the d-block and f-block elements.

d-block

The large middle section of the periodic table (groups 3–12) where the (n−1)d orbitals are progressively filled.

f-block

The bottom panel containing the 4f and 5f orbitals progressively filled; comprises the inner transition metals.

transition metals

Metals with incompletely filled d subshells in their atoms or ions; excludes Zn, Cd, and Hg which have full d10 in the ground state.

inner transition metals

Elements with progressively filled 4f (lanthanoids) or 5f (actinoids) orbitals; treated as a separate block.

lanthanoids

The 4f-series (Ce to Lu); typically show +3 oxidation state and exhibit lanthanoid contraction.

actinoids

The 5f-series (Th to Lr); show a wide range of oxidation states and are largely radioactive.

lanthanoid contraction

Regular decrease in atomic/ionic radii across the lanthanide series due to imperfect shielding by 4f electrons.

actinoid contraction

Contraction in the radii of actinoids, generally larger variation than lanthanoids, due to shielding by 5f electrons.

3d-series

The first transition metal series: Sc to Zn.

4d-series

The second transition metal series: Y to Cd.

5d-series

The third transition metal series: La and Hf to Hg.

6d-series

The fourth transition series: Ac and elements from Rf to Cn.

outer-electron configuration (d-block)

General outer electronic configuration (n−1)d1–10 ns1–2; with Pd as an exception (4d10 5s0).

Cr and Cu anomalies

Cr often shows 3d5 4s1; Cu shows 3d10 4s1 instead of 3d9 4s2 due to small energy gaps and stability of half-filled or filled subshells.

Zn, Cd, Hg not true transition metals

Have complete d10 in ground state; end members of 3d, 4d, 5d series but chemistry is treated with transition metals.

melting point trend (transition metals)

Generally high melting points; rise to a maximum around d5; Mn and Tc are anomalous.

enthalpy of atomisation

Energy required to convert a solid metal into gaseous atoms; high for transition metals due to strong interatomic bonding.

atomic/ionic radii trends in a series

Within a series, radii decrease with increasing Z because d electrons shield poorly; lanthanoid contraction makes 2nd and 3rd series radii similar.

density trend (early transition metals)

Density increases from Ti to Cu due to lanthanoid-like contraction and mass increment, leading to closely similar radii and higher mass.

ionisation enthalpies in 3d series

First ionisation enthalpy generally increases left to right; second/third ionisation enthalpies rise sharply; Cr and Cu show breaks due to half-filled and full d configurations.

Hund’s rule and exchange energy

Hund’s rule favors maximum unpaired spins in degenerate orbitals; exchange energy stabilizes certain dn configurations (e.g., d5, d10).

d-block oxidation-state variability

Huge range of common oxidation states (e.g., Mn from +2 to +7); end elements like Sc and Zn have more limited common states.

highest oxidation states and ligands

Highest oxidation states are stabilized by ligands (often F−); fluorides like CrF6, VF5 illustrate strong stabilization by ligands.

oxidation states in oxides and oxoanions

Highest oxidation state often coincides with group number in oxides (e.g., Mn in Mn2O7, Cr in CrO3, V in V2O5).

chromates/dichromates

Chromate (CrO4^2−) and dichromate (Cr2O7^2−) equilibrate with pH; interconvertible in water; acidification converts chromate to dichromate; strong oxidants.

preparation of potassium dichromate

From chromite ore (FeCr2O4) fused with Na/K carbonate, chromate is formed and converted to dichromate by acidification; later exchange yields K2Cr2O7.

potassium permanganate (KMnO4)

Strong oxidizing agent prepared from MnO2; disproportionates to permanganate; widely used in analytical and organic chemistry.

coloured ions (d-block)

Many transition metal ions are colored due to d–d transitions; colors depend on ligands and oxidation state.

formation of complex compounds

Transition metals form numerous complexes due to small size, high charge, and available d orbitals (e.g., [Fe(CN)6]^3−, [Cu(NH3)4]^2+).

interstitial compounds

Compounds formed when small atoms (H, C, N) occupy interstitial sites in metal lattices; non-stoichiometric, very hard with high mp (e.g., TiC, TiH1.7).

alloys

Mixtures or solid solutions of metals that are typically hard with high melting points (e.g., steels; mischmetall is a lanthanide-containing alloy).

catalytic properties of d-/f-blocks

Many transition metals catalyze reactions due to multiple oxidation states and complex formation (e.g., V2O5 in Contact Process, Fe in Haber, Ni in hydrogenation, PdCl2 in Wacker).

coloured transition metal ions (examples)

Colors arise from electronic transitions; specific colors listed for various ions in aqueous solution (e.g., V4+, Mn2+, Cu2+).

lanthanoids oxidation states

Mostly +3; some show +4 or +2 in certain contexts; Ce4+ stabilized by noble-gas configuration; Eu2+ and Yb2+ show +2 in some compounds.

actinoids oxidation states

Wider range of oxidation states; +3 common; early actinoids show higher states; many are radioactive; bonding involves 5f, 6d, 7s orbitals.

magnetic properties of d-/f-blocks

Many transition metals are paramagnetic due to unpaired electrons; spin-only magnetic moment μ = sqrt(n(n+2)) in Bohr magnetons; examples show varying n.

standard electrode potentials (M2+/M and M3+/M2+)

E° values indicate tendency to be reduced; trend across 3d series shows Mn/Ni/Zn particularly negative for M2+/M; Cu is +0.34 V for M2+/M; Ce4+/Ce3+ is +1.74 V.

disproportionation

A process where an element in an intermediate oxidation state forms two species of different oxidation states (one higher, one lower); e.g., Mn species or similar examples in text.

summary takeaway

The d- and f-block elements show characteristic metallic properties, wide oxidation-state variability, complex formation, and catalytic activity; lanthanoids/actinoids exhibit contraction effects influencing subsequent elements.