Chapter-4 D and F-Block Elements

Comprehensive vocabulary flashcards covering the key terms, definitions, trends, and chemical reactions of d-block and f-block transition elements.

D-Block Elements

Elements in which the valence electron enters into the penultimate shell ($d$-subshell). They belong to groups $3-12$ in the periodic table.

Transition Elements

Elements that have an incompletely filled $d$-subshell in their elemental state and/or in any one oxidation state.

General Electronic Configuration of D-Block Elements

$$(n-1)d^{1-10}ns^{0-2}$$

Non-Transition D-Block Elements ($Zn$, $Cd$, $Hg$)

Elements not considered transition elements due to the absence of an incompletely filled $d$-subshell in both their elemental state and oxidation states.

High Melting Point of Transition Metals

A characteristic caused by strong interatomic metallic bonding due to a greater number of valence electrons.

Trend in Melting Point Across a Transition Series

Increases to a maximum (at $Cr$ due to the maximum number of unpaired electrons) and then decreases regularly ($Fe$ onwards due to pairing of electrons), with an exception at Manganese ($Mn$) due to its stable half-filled configuration.

Enthalpy of Atomization ($\Delta_a H^\circ$) Trend

Follows the order $5d > 4d > 3d$, increasing down a group due to increased strength of interatomic metallic bonding, with Tungsten ($W$) having a very high value.

Variable Oxidation States of Transition Metals

The ability to exhibit multiple oxidation states due to the participation of both $ns$ and $(n-1)d$ electrons, which are similar in energy.

Maximum Oxidation State in Transition Elements

$+8$, exhibited by Osmium ($Os$) in $OsO_4$ and Ruthenium ($Ru$) in $RuO_4$.

Spin-Only Formula

$\mu = \sqrt{n(n+2)}\,\text{BM}$, where $n$ is the number of unpaired electrons and $\text{BM}$ is Bohr Magneton.

Paramagnetic vs. Diamagnetic Configurations

$d^1-d^9$ configurations are paramagnetic due to the presence of unpaired electrons, whereas $d^0$ and $d^{10}$ configurations are diamagnetic due to the absence of unpaired electrons.

d-d Transition

The excitation of an electron between split lower-energy and higher-energy $d$-subshells upon light absorption in the visible region, giving rise to colored transition metal compounds.

Color in $KMnO_4$ and $K_2Cr_2O_7$

Intense coloration caused by charge transfer from ligand to metal rather than $d$-$d$ transitions.

Bronze

An alloy composed of Copper and Tin ($Cu + Sn$).

Brass

An alloy composed of Copper and Zinc ($Cu + Zn$).

German Silver

An alloy composed of Copper, Nickel, and Zinc ($Cu + Ni + Zn$).

Interstitial Compounds

Compounds formed by the accommodation of smaller atoms like hydrogen, carbon, boron, and nitrogen into the interstitial voids of a transition metal lattice (e.g., $Fe_3H$, $TiC$, $Mn_4N$).

Properties of Interstitial Compounds

Harder than the parent metal (especially borides), have higher melting points than the parent metal, are chemically inert (less reactive), and retain metallic conductivity.

Catalytic Properties of Transition Metals

Arises from their ability to adopt variable oxidation states during reactions and the availability of vacant $d$-subshells to provide active sites.

Chromite Ore

The starting material ($FeCr_2O_4$) used in the industrial three-step preparation of potassium dichromate ($K_2Cr_2O_7$).

Chromate Ion ($CrO_4^{2-}$)

A yellow, tetrahedral oxoanion of chromium that predominates in basic medium.

Dichromate Ion ($Cr_2O_7^{2-}$)

An orange-red oxoanion consisting of two tetrahedral units linked by a $Cr-O-Cr$ bond, which predominates in acidic medium.

Pyrolusite Ore

The manganese ore ($MnO_2$) used in the preparation of potassium permanganate ($KMnO_4$) via alkaline oxidative fusion.

Manganate Ion ($MnO_4^{2-}$)

A dark green, tetrahedral ion of manganese formed during the intermediate stage of $KMnO_4$ synthesis.

Permanganate Ion ($MnO_4^-$)

A purple, tetrahedral oxoanion of manganese obtained by electrolytic oxidation or acidification of the manganate ion.

Baeyer's Reagent

Alkaline potassium permanganate ($KMnO_4$) used as a reagent and oxidizing agent.

F-Block Elements (Inner-Transition Elements)

Elements in which the last electron enters into the anti-penultimate shell ($f$-subshell), having the general electronic configuration $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$.

Lanthanoid Contraction

The steady decrease in atomic and ionic radii across the lanthanoid series with increasing atomic number, caused by the poor shielding effect of $4f$ electrons.

Consequences of Lanthanoid Contraction

Similar atomic sizes of second ($4d$) and third ($5d$) transition series elements (e.g., $Zr$ and $Hf$), difficulty in separating individual lanthanoids, and decrease in basic strength of hydroxides from $La(OH)_3$ to $Lu(OH)_3$.

Mischmetal

A commercially important alloy consisting of approximately $95\%$ lanthanoid metals, $5\%$ iron ($Fe$), and traces of $S$, $C$, $Ca$, and $Al$, used to produce bullets, shells, and lighter flints.

Actinoid Contraction

The gradual decrease in atomic and ionic radii across the actinoid series, which is greater from element to element than lanthanoid contraction due to poorer shielding by $5f$ electrons compared to $4f$ electrons.

Wacker Process

An industrial catalytic application of $d$-block elements where ethyne is oxidized to ethanal using $PdCl_2$ as a catalyst.

Disproportionation of $Cu^+$

The aqueous instability of $Cu^+$ where it spontaneously undergoes disproportionation into $Cu^{2+}$ and $Cu$: $2Cu^+ \rightarrow Cu^{2+} + Cu$.