d- and f-Block Elements - Practice Questions with Answers

Q1.

Transition metals are found in which block of the periodic table?

• A d-block
• B s-block
• C p-block
• D f-block

Q2.

Which property is characteristic of transition metals?

• A Variable oxidation states
• B Fixed single oxidation state
• C No colour in compounds
• D Non-magnetic

Q3.

What colour is the KMnO₄ (potassium permanganate) solution?

• A Purple/violet
• B Yellow
• C Green
• D Colourless

Q4.

Which transition metal is used as a catalyst in the Haber process?

• A Iron (Fe)
• B Platinum (Pt)
• C Vanadium (V)
• D Nickel (Ni)

Q5.

Which transition metal is used in the catalytic converter in cars?

• A Platinum (Pt) and Palladium (Pd)
• B Iron, valued for its low cost in oxidation catalysis
• C Zinc, commonly used as a sacrificial anode in galvanising
• D Copper, prized for its high electrical conductivity in wiring

Q6.

The colour of transition metal compounds is due to:

• A d-d electron transitions absorbing visible light
• B Their characteristically high melting points compared to main-group salts
• C Their predominantly ionic character in the solid lattice
• D Their general paramagnetic or ferromagnetic behaviour

Q7.

Which transition metal is liquid at room temperature?

• A Mercury (Hg)
• B Zinc
• C Iron
• D Nickel

Q8.

The electronic configuration of Cu is [Ar]3d¹⁰ 4s¹ (anomalous). This is because:

• A Fully filled d¹⁰ is extra stable
• B It has odd atomic number under usual circumstances
• C 3d orbitals are empty according to most researchers
• D It is a noble gas in the majority of cases studied

Q9.

Which transition metal is the best conductor of electricity?

• A Silver (Ag)
• B Copper (Cu)
• C Gold (Au)
• D Aluminium (Al)

Q10.

The lanthanides are also called:

• A Rare earth metals
• B Alkaline earth metals
• C Transition metals
• D Noble metals

Q11.

Which element is called the 'king of metals' due to its nobility?

• A Gold (Au)
• B Silver (Ag)
• C Platinum (Pt)
• D Iron (Fe)

Q12.

Rust is formed when iron reacts with:

• A Oxygen and water (moist air)
• B Carbon dioxide gas dissolved in dry air
• C Nitrogen gas present in the surrounding atmosphere
• D Dilute hydrochloric acid splashed onto the surface

Q13.

Which transition metal is essential for haemoglobin?

• A Iron (Fe²⁺)
• B Zinc
• C Copper
• D Manganese

Q14.

K₂Cr₂O₇ (potassium dichromate) has which colour?

• A Orange
• B Purple
• C Blue
• D Green

Q15.

Which transition metal is used to galvanise iron?

• A Zinc (Zn)
• B Tin (Sn)
• C Nickel (Ni)
• D Chromium (Cr)

Q16.

Transition metals generally have high melting points because:

• A Strong metallic bonding involving both s and d electrons
• B A significant degree of ionic character within the metallic lattice
• C Their unusually large atomic masses compared to main-group metals
• D Their underlying noble gas electron configuration

Q17.

Which element is used as the filament in incandescent light bulbs?

• A Tungsten (W)
• B Iron
• C Molybdenum
• D Nickel

Q18.

Which f-block elements are radioactive?

• A All actinides
• B All lanthanides
• C Mainly uranium
• D Mainly thorium

Q19.

Uranium is used in:

• A Nuclear fuel and nuclear weapons
• B Industrial catalysts for hydrogenation reactions
• C Stainless steel alloys requiring corrosion resistance
• D Permanent magnets used in electric motors

Q20.

Which transition metal is used in stainless steel?

• A Chromium (Cr)
• B Copper
• C Zinc
• D Tin

Q21.

The electronic configuration of Cr is [Ar]3d⁵ 4s¹ rather than [Ar]3d⁴ 4s² because:

• A Half-filled d⁵ is extra stable due to exchange energy and symmetry
• B The 3d subshell is usually filled largely before the 4s subshell
• C Chromium is a diamagnetic element with little unpaired electrons
• D The 4s subshell must usually retain exactly two electrons under most conditions encountered

Q22.

Crystal field theory (CFT) explains colour and magnetic properties. In an octahedral field, d orbitals split into:

• A t_2g (lower energy, 3 orbitals) and eg (higher energy, 2 orbitals)
• B Two perfectly equal-energy sets of orbitals with no splitting at all
• C Three separate sets of orbitals all at different energy levels
• D An unpredictable, random pattern of orbital energies

Q23.

A complex with 3 unpaired electrons is:

• A Paramagnetic (attracted to magnetic field)
• B Diamagnetic and therefore weakly repelled by a magnetic field
• C Completely non-magnetic with zero interaction with a field
• D Antiferromagnetic with perfectly cancelling adjacent spins

Q24.

Which species is diamagnetic?

• A Zn²⁺ ([Ar]3d¹⁰, all paired)
• B Fe³⁺ ([Ar]3d⁵) in typical laboratory settings
• C Cu²⁺ ([Ar]3d⁹) under usual circumstances
• D Mn²⁺ ([Ar]3d⁵) according to most researchers

Q25.

What is the spin-only magnetic moment formula?

• A mu = sqrt(n(n+2)) Bohr magnetons, where n = number of unpaired electrons
• B mu = n Bohr magnetons, scaling linearly with unpaired electron count
• C mu = n² Bohr magnetons, scaling with the square of electron count
• D mu = 2n Bohr magnetons, simply doubling the unpaired electron count

Q26.

The Cr₂O₇^2- ion in acidic solution is a strong oxidising agent because:

• A Cr is reduced from +6 to +3, releasing 3e- per Cr atom (6e- total per formula unit)
• B The dichromate ion is itself generally an acidic species in solution in the majority of cases studied
• C Chromium is oxidised from its elemental state of 0 up to +6 as widely reported
• D No actual electron transfer occurs during this redox reaction in standard practice

Q27.

Lanthanide contraction refers to:

• A Progressive decrease in atomic/ionic radii from La to Lu due to poor shielding by 4f electrons
• B A steady increase in both atomic and ionic radii moving from La all the way to Lu
• C The spontaneous radioactive decay process observed uniformly across the whole lanthanide series
• D The gradual stepwise loss of all fourteen 4f electrons moving from La through to Lu

Q28.

The consequence of lanthanide contraction is that:

• A 5d elements (Period 6) are nearly the same size as 4d elements (Period 5) in the same group
• B All fifteen lanthanide elements end up with completely identical chemical properties
• C The entire d-block of the periodic table physically contracts in size
• D The lanthanide elements become progressively larger across the series

Q29.

Which transition metal shows the highest oxidation state (+8)?

• A Osmium (OsO₄) and Ruthenium (RuO₄)
• B Iron, which is most stable in the +2 and +3 oxidation states
• C Manganese, whose highest common oxidation state is +7
• D Chromium, whose highest common oxidation state is +6

Q30.

In the variable oxidation states of Mn, the most stable in acidic aqueous solution is:

• A Mn²⁺
• B Mn³⁺
• C MnO₄^-
• D MnO₄^2-

Q31.

Which complex shows the most intense colour in crystal field theory?

• A Complex with large crystal field splitting (strong field ligands)
• B A complex showing only a small crystal field splitting energy
• C Any diamagnetic complex regardless of its splitting energy
• D A complex with an empty d⁰ configuration and no d electrons to excite

Q32.

The spectrochemical series arranges ligands by:

• A Increasing field strength: I- < Br- < Cl- < F- < OH- < H₂O < NH₃ < en < CN-
• B Decreasing atomic mass of the donor atom across the ligand series under most conditions encountered
• C Charge on the ligand alone, independent of donor atom identity as frequently observed in practice
• D Physical size of the ligand alone, independent of field strength in many documented cases

Q33.

Interstitial compounds of transition metals with C, N, or H are:

• A Hard, high melting point, conduct electricity but chemically inert (e.g., TiC, WC)
• B Simple ionic compounds held together by electrostatic lattice forces according to conventional understanding
• C Discrete molecular compounds with well-defined low melting points in routine practice
• D Readily soluble compounds that dissolve largely in water overall in most cases

Q34.

Which test distinguishes Fe²⁺ from Fe³⁺?

• A KSCN gives blood-red with Fe³⁺ (FeSCN2+); no colour with Fe²⁺; K₄[Fe(CN)₆] gives Turnbull's blue with Fe³⁺
• B Both Fe²⁺ and Fe³⁺ are said to give an identical colour reaction with every common test reagent under typical conditions
• C A simple pH measurement taken of the dissolved iron salt solution alone according to standard textbooks
• D A standard flame test performed by observing the colour of the emitted light in general practice as frequently described

Q35.

Catalytic activity of transition metals is due to:

• A Ability to change oxidation states and provide active surface for adsorption
• B Their generally high molecular or atomic mass compared to other metals
• C Their predominantly ionic character in the bulk metallic state
• D Their underlying noble gas electron configuration

Q36.

The actinide series fills which orbitals?

• A 5f orbitals (from Ac, Z=89 to Lr, Z=103)
• B 4f orbitals, the same set filled by the lanthanide series
• C 6d orbitals, filled instead in the subsequent transactinide series
• D 7s orbitals, which are already filled before the actinides begin

Q37.

Which transition metal is used in the Contact process as a catalyst?

• A Vanadium(V) oxide (V₂O₅)
• B Iron, the catalyst used instead in the Haber process for ammonia
• C Platinum, the catalyst used instead in the Ostwald process for nitric acid
• D Nickel, the catalyst used instead in the hydrogenation of vegetable oils

Q38.

Transition metals form alloys easily because:

• A Similar atomic radii allow atoms to substitute for each other in the metallic lattice
• B Strong ionic bonding forms directly between the two different metal atoms in most textbook accounts
• C Every transition metal happens to share an identical valence electron count during normal conditions
• D All transition metals possess exactly two valence electrons each as generally observed

Q39.

The colour change of K₂Cr₂O₇ from orange to yellow on adding NaOH is due to:

• A Cr₂O₇^2- (orange, acidic) converting to CrO₄^2- (yellow, basic)
• B A reduction of chromium from the +6 to the +3 oxidation state
• C An oxidation of chromium to an even higher oxidation state than +6
• D A simple temperature change caused by mixing the two solutions

Q40.

The Ziegler-Natta catalyst contains which transition metal?

• A Titanium (TiCl₄) with organoaluminium compound
• B Iron, paired with an organoaluminium co-catalyst instead
• C Cobalt, paired with an organoaluminium co-catalyst instead
• D Platinum, paired with an organoaluminium co-catalyst instead

Q41.

Using crystal field theory, predict whether [Co(NH₃)₆]3+ is high spin or low spin:

• A Low spin: NH₃ is a strong field ligand, large Delta causes electron pairing (t_2g⁶, 0 unpaired)
• B High spin, since NH₃ behaves as a weak field ligand toward cobalt(III) under most conditions encountered
• C Paramagnetic with four unpaired electrons distributed across t_2g and eg as frequently observed in practice
• D An outcome that cannot be predicted from crystal field theory in many documented cases according to conventional understanding

Q42.

The crystal field stabilisation energy (CFSE) for d³ in an octahedral field is:

• A -1.2 Delta_o (three electrons each in t_2g, each contributing -0.4 Delta_o)
• B Zero, since a d³ configuration shows no net stabilisation in routine practice
• C +1.2 Delta_o, a positive destabilisation for this configuration overall
• D -0.8 Delta_o, corresponding instead to a d2 configuration in most cases

Q43.

The Jahn-Teller effect in Cu²⁺ complexes (d⁹) causes:

• A Distortion of the octahedral geometry (elongation along z-axis due to unequal occupation of eg orbitals)
• B No distortion, leaving the geometry as a perfectly regular octahedron in every case under typical conditions
• C A complete rearrangement of the ligands into an largely trigonal prismatic geometry instead according to standard textbooks
• D An overall increase in complex stability while the octahedral geometry stays perfectly regular in general practice

Q44.

Which of the following complexes does NOT show Jahn-Teller distortion?

• A [Co(NH₃)₆]3+ (d⁶, low spin, t_2g⁶ = symmetric)
• B [Cu(H₂O)6]2+ (d⁹)
• C [Mn(H₂O)6]3+ (d⁴ high spin)
• D [CrF6]3- (d³)

Q45.

The 18-electron rule in organometallics states that:

• A Stable transition metal complexes have 18 electrons in the valence shell (sum of metal d electrons + ligand electrons)
• B Every transition metal atom is said to contain exactly 18 neutrons within its nucleus as frequently described in most textbook accounts
• C A maximum of 18 separate individual ligands can ever coordinate to one single metal centre during normal conditions
• D Transition metals are said to be capable of exhibiting up to 18 distinct oxidation states as generally observed in typical laboratory settings

Q46.

Fe(CO)₅ is a stable organometallic compound. The oxidation state of Fe in Fe(CO)₅ is:

• A 0 (CO is a neutral ligand)
• B 2+, since each CO ligand is treated as a -2/5 charge donor
• C 3+, matching iron's most common oxidation state in its salts
• D -2, as iron is formally reduced by the five CO ligands

Q47.

The trans-influence in square planar complexes refers to:

• A Weakening of the bond trans to a strong trans-influencing ligand (strong sigma donor weakens trans bond)
• B A simple shift in the colour the square planar complex visibly displays under usual circumstances according to most researchers
• C A measurable change observed in the complex's overall magnetic moment instead in the majority of cases studied
• D The complete absence of any measurable effect whatsoever on the trans bond strength as widely reported

Q48.

Which of the following metal ions will form colourless complexes?

• A Sc3+ (d⁰) and Ti4+ (d⁰) and Zn²⁺ (d¹⁰)
• B Fe³⁺ (d⁵), which gives pale yellow complexes from a spin-forbidden d-d transition
• C Cu²⁺ (d⁹), which gives characteristically blue complexes
• D Ni²⁺ (d⁸), which gives characteristically green complexes

Q49.

The effective atomic number (EAN) rule is satisfied by [Ni(CO)₄]. Ni has which electron count in this complex?

• A 18 (Ni: 10 d+4s electrons; 4 CO donate 2e each = 8; total 10+8=18)
• B 16, the electron count typical of square planar d⁸ complexes instead
• C 20, an electron count that would exceed the stable noble gas total
• D 12, an electron count well below the stable 18-electron configuration

Q50.

Lanthanide ions (Ln3+) are less coloured than transition metals because:

• A 4f orbitals are well-shielded and inner; f-f transitions are Laporte-forbidden and very weak
• B Lanthanide ions largely lack any d orbitals in their electron configuration in standard practice
• C Lanthanide ions are uniformly diamagnetic with little unpaired electrons under most conditions encountered
• D Lanthanide ions characteristically adopt unusually high oxidation states as frequently observed in practice

Q51.

Nuclear fission of 235U is initiated by:

• A Slow (thermal) neutrons captured by the nucleus
• B High-energy fast neutrons exclusively, since slow neutrons cannot be captured
• C High-energy gamma ray photons absorbed by the nucleus
• D Alpha particles fired directly at the uranium nucleus

Q52.

The trans effect in square planar Pt(II) complexes is used to synthesise:

• A Cisplatin [cis-Pt(NH₃)₂Cl₂] by exploiting that Cl- has stronger trans-labilising effect than NH₃
• B A largely random, loosely controlled mixture of cis and trans geometric isomers in many documented cases
• C Mainly the trans isomer of the platinum complex with little cis product formed according to conventional understanding
• D Octahedral platinum complexes formed instead of the intended square planar product in routine practice

Q53.

Ferromagnetism (as in iron) occurs because:

• A Unpaired electrons in adjacent atoms align parallel in magnetic domains (quantum exchange coupling)
• B A significant degree of ionic character present throughout the bulk metal lattice in many documented cases
• C The simple presence of a very large total number of electrons within each metal atom according to conventional understanding
• D The metal's characteristically high melting point compared to other transition metals in routine practice

Q54.

What is the difference between lanthanides and actinides in terms of chemical behaviour?

• A Actinides show greater variety of oxidation states (due to 5f, 6d and 7s close in energy) vs lanthanides (predominantly +3)
• B There is said to be essentially no meaningful chemical difference between the two series overall in most cases under typical conditions
• C Actinides are said to be largely non-radioactive elements, unlike the well-known lanthanides according to standard textbooks
• D Lanthanides are said to characteristically show a far wider range of oxidation states than actinides in general practice

Q55.

The Bohr magneton (BM) is the unit of magnetic moment. The spin magnetic moment is given by mu = sqrt(n(n+2)). For Fe³⁺ (d⁵, high spin), mu =

• A 5.92 BM (n=5 unpaired electrons)
• B 3.87 BM, the value corresponding instead to three unpaired electrons
• C 1.73 BM, the value corresponding instead to a single unpaired electron
• D 2.83 BM, the value corresponding instead to two unpaired electrons

Q56.

Which transition metal complex is used as an anti-cancer drug?

• A Cisplatin [cis-Pt(NH₃)₂Cl₂]
• B K2[PtCl₄] as frequently described
• C [Co(NH₃)₆]Cl3 in most textbook accounts
• D [Fe(CN)₆]4- during normal conditions

Q57.

Why do transition metals and their compounds act as catalysts for many industrial reactions?

• A They have accessible multiple oxidation states that allow electron transfer cycles, and they can adsorb and activate substrates
• B Catalytic activity is said to generally correlate with how expensive each particular metal happens to be as generally observed
• C Their generally large atomic weights are what is said to account for their catalytic ability in typical laboratory settings
• D Every transition metal catalyst is said to necessarily be an inherently paramagnetic species under usual circumstances according to most researchers

Q58.

The crystal field splitting in octahedral (Delta_o) vs tetrahedral (Delta_t) field: which is larger?

• A Octahedral (Delta_o = 9/4 Delta_t); octahedral complexes have much larger splitting
• B Tetrahedral splitting, which exceeds octahedral splitting for the same ligand
• C Both geometries give numerically identical splitting energies
• D The relative splitting depends solely on the ligand and not on geometry

Q59.

In the disproportionation of MnO₄^2- in acidic solution:

• A 3MnO₄^2- + 4H+ → 2MnO₄^- + MnO₂ + 2H₂O (Mn goes from +6 to +7 and +4)
• B Manganese remains largely in the +6 oxidation state throughout
• C Manganese is largely reduced down to the +2 oxidation state during normal conditions
• D No reaction occurs when MnO₄^2- is acidified as generally observed

Q60.

The magnetic moment of a complex ion can be used to determine:

• A Number of unpaired electrons (and thus high-spin vs low-spin configuration)
• B The exact charge carried by each coordinated ligand
• C The metal's oxidation state read off directly without any calculation
• D The precise colour the complex will display in solution