Comparison Tables & Long-Answer Questions

CHEExam Practice & Reasoning

These are structured long-answer items: one-line reasons, short notes, and side-by-side comparisons of $d$ -block and $f$ -block elements. Answers should be organised under the given headings and stay crisp.

$Mn$ shows the most oxidation states ( $+2$ to $+7$ ) in the $3d$ series because it has the maximum number of unpaired $3d$ plus $4s$ electrons ( $3d^5 4s^2$ ) available for bonding.
Transition-metal atomic radii vary little across a period (unlike s-block metals) because the poorly shielding $d$ electrons offset the rising nuclear charge.
Short notes essentials — interstitial compounds: hard, high-melting, metallic, non-stoichiometric; alloys: substitutional, harder and corrosion-resistant; catalysis: due to variable oxidation states and surface adsorption.
$d$ - vs $f$ -block: $d$ -block fills the $(n-1)d$ subshell while $f$ -block (inner transition) fills the $(n-2)f$ subshell.
$d$ -block shows many oxidation states with marked variation across a series; lanthanoids are predominantly $+3$ with a far narrower range of states.
Colour in $d$ -block ions is mainly from $d\text{-}d$ transitions (partly filled $d$ ); in lanthanoid ions it is from shielded $f\text{-}f$ transitions, giving pale, sharp-line colours.
Charge-transfer spectra: in $MnO_4^-$ and $Cr_2O_7^{2-}$ ( $d^0$ centres) the intense colour comes from electron transfer from oxygen to the metal, not from $d\text{-}d$ transitions, hence the very strong absorption.
Magnetic behaviour: most $d$ -block ions are paramagnetic from unpaired $d$ electrons (spin-only $\mu = \sqrt{n(n+2)}$ ); lanthanoid ions also include an orbital contribution, so spin-only values fit them less well.
Examples and uses: $Fe$ (Haber catalyst, structural steel), $V_2O_5$ (Contact process), $Ni$ (hydrogenation), $TiO_2$ (white pigment); lanthanoids — $Ce$ in misch-metal/lighter flints, $Nd$ in strong magnets.
Across a comparison table, contrast $d$ - and $f$ -block under: subshell filled, range of oxidation states, origin of colour, magnetic behaviour, and characteristic examples/uses.
When asked for 'reasons', give one crisp cause-and-effect sentence per point; for 'short notes', give 2–3 key defining features each.

Where the marks go

Stating the $f$ -block fills the $(n-1)f$ subshell; inner-transition elements fill the $(n-2)f$ subshell.
Attributing lanthanoid colour to $d\text{-}d$ transitions; it arises from shielded $f\text{-}f$ transitions giving pale, sharp lines.
Calling $MnO_4^-$ / $Cr_2O_7^{2-}$ colour a $d\text{-}d$ effect in a comparison table; with $d^0$ centres it is charge transfer.
Writing rambling paragraphs for 'reasons' questions; each reason should be a single precise sentence linking cause to effect.
Saying lanthanoids show as many oxidation states as $d$ -block metals; lanthanoids are overwhelmingly $+3$ with a much narrower range.

How the board asks it

Distinguishd- vs f-block contrasts
Compare the $d$ -block and $f$ -block elements under the following headings: (i) subshell filled, (ii) range of oxidation states, (iii) origin of colour, and (iv) magnetic behaviour.
Give reasonsvariable oxidation states and atomic-radii trends
Give reasons: (i) $Mn$ shows the maximum number of oxidation states ( $+2$ to $+7$ ) in the $3d$ series. (ii) Atomic radii of the transition metals vary only slightly across a period.
Define / stateinterstitial compounds, alloys, catalysis
Write short notes on any two of the following, giving their key defining features: (i) interstitial compounds, (ii) alloys, (iii) catalytic action of transition metals.
Give reasonscharge-transfer spectra in $d^0$ ions
Account for the intense colour of $KMnO_4$ and $K_2Cr_2O_7$ even though the metal centre in each is $d^0$ .
Distinguishd-d vs f-f transitions
Compare the origin of the colour of a typical $d$ -block ion such as $Cu^{2+}$ with that of a lanthanoid ion such as $Pr^{3+}$ , accounting for the difference in each case.
Applicationcharacteristic catalysts, pigments and lanthanoid applications
State one important use each of the following: (i) $V_2O_5$ , (ii) $TiO_2$ , (iii) $Fe$ , and (iv) $Ce$ in misch-metal.

PreviousGeneral Properties: Reasoning Questions

Written for Sublevo. Question text quoted anywhere in these notes is the Council’s and carries its year and paper; the board’s own diagrams are not reproduced.