Free NEET Chemistry multiple-choice questions on Lanthanoids & Actinoids. Attempt each question and reveal the answer with a full explanation.
What is the general electronic configuration of Lanthanoids? [Xe] 4f 1-14 5d 0-1 6s 2 [Xe] 4f 0-14 5d 1 6s 2 [Xe] 5f 1-14 6d 0-1 7s 2 [Xe] 4f 1-14 5d 2 6s 2 Which of the following elements is used in the manufacture of high-strength permanent magnets (e.g., in computer hard drives)? Neodymium (Nd) Cerium (Ce) Lanthanum (La) Gadolinium (Gd) Among the following, which one is a member of the actinoid series? Thorium ( Th ) Gadolinium ( Gd ) Lanthanum ( La ) Lutetium ( Lu ) The radioactive lanthanoid element is: Promethium Samarium Dysprosium Holmium More number of oxidation states are exhibited by the actinoids than by the lanthonoids. The main reason for this is:- More energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals Lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals Greater metallic character of the lanthanoids than that of the corresponding actinoids More active nature of the actinoids Identify the incorrect statement among the following: Lanthanoid contraction is the accumulation of successive shrinkages. As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements. Shielding power of 4f electrons is quite weak. There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu. Reason of lanthanoid contraction is :- Negligible screening effect of 'f' orbitals Increasing nuclear charge Decreasing nuclear charge Decreasing screening effect Zr (Z = 40) and Hf (Z = 72) have similar atomic and ionic radii because of : Diagonal relationship Lanthanoid contraction Having similar chemical properties Belonging to same group Although +3 oxidation state is most common in lanthanoids, cerium still shows +4 oxidation state because: After losing one more electron, it acquires 4f 14 electronic configuration. Its nearest inert gas is Radon. After losing one more electron, it acquires 4f 0 electronic configuration. Its atomic number is 61. The reason for greater range of oxidation states in actinoids than in lanthanoids is: the 5f, 6d and 7s levels having comparable energies actinoids being more reactive than lanthanoids the 4f and 5d levels being close in energies radioactive nature of actinoids Which of the following statements about the Eu 2+ ion is correct? It acts as a strong reducing agent It is a strong oxidizing agent It is colorless It is diamagnetic Which alloy contains approximately 95 % lanthanoid metal and 5 % iron, along with traces of S, C, Ca, and Al ? Mischmetall Brass Bronze Invar Which of the following lanthanoid elements is obtained synthetically (radioactive)? Promethium ( Pm ) Samarium ( Sm ) Neodymium ( Nd ) Terbium ( Tb ) Identify the correct order of the size of the following ions: La 3+ > Ce 3+ > Pr 3+ > Lu 3+ Lu 3+ > Pr 3+ > Ce 3+ > La 3+ Ce 3+ > La 3+ > Pr 3+ > Lu 3+ Pr 3+ > Lu 3+ > Ce 3+ > La 3+ What is the correct order of the basicity of the following lanthanoid hydroxides? La(OH) 3 > Gd(OH) 3 > Lu(OH) 3 Lu(OH) 3 > Gd(OH) 3 > La(OH) 3 Gd(OH) 3 > La(OH) 3 > Lu(OH) 3 La(OH) 3 > Lu(OH) 3 > Gd(OH) 3 Which of the following lanthanoids shows a stable +4 oxidation state? Ce Eu Yb La Identify the incorrect statement regarding the comparison of Lanthanoids and Actinoids. Lanthanoids show a greater range of oxidation states than Actinoids Actinoids are radioactive while most Lanthanoids are not The magnetic properties of Actinoids are more complex than Lanthanoids The 5f electrons have poorer shielding effect than 4f electrons Which lanthanoid ion is used as a powerful oxidizing agent in analytical chemistry? Ce 4+ Eu 2+ Tb 4+ Yb 2+ Which of the following statements is correct regarding the complexing tendency of lanthanoids and actinoids? Actinoids have a greater tendency to form complexes than lanthanoids. Lanthanoids have a greater tendency to form complexes than actinoids. Both have an equal tendency to form complexes. Neither lanthanoids nor actinoids form coordination complexes. The stability of the +2 oxidation state for Eu ( Z=63 ) and Yb ( Z=70 ) is due to: Half-filled and completely-filled f -subshells Lanthanoid contraction High third ionization enthalpy Large atomic size The actinoid contraction is greater from element to element than lanthanoid contraction because: 5f electrons have poorer shielding than 4f electrons 5f electrons have better shielding than 4f electrons The nuclear charge of actinoids is lower Actinoids have more d -electrons Lanthanoid contraction is primarily caused by: Imperfect shielding of one 4f electron by another Increased nuclear charge only The shape of the s -orbitals Effective shielding of 4f by 5d electrons Which of the following statements is FALSE regarding the actinoids? All actinoids are non-radioactive They show a wider range of oxidation states than lanthanoids The actinoid contraction is greater from element to element than lanthanoid contraction Most actinoid ions are colored Which lanthanoid element is used extensively in the production of alloy steels for making plates and pipes? Cerium ( Ce ) Lutetium ( Lu ) Promethium ( Pm ) Gadolinium ( Gd ) Which of the following is the most basic oxide? La 2O 3 Lu 2O 3 Sm 2O 3 Gd 2O 3 Which of the following statements regarding the reactivity of Lanthanoids is FALSE? They do not react with water even at boiling temperatures. They react with H 2 on gentle heating to form hydrides. They burn in oxygen to form Ln 2O 3 . They liberate H 2 gas when reacted with dilute acids. The basic strength of the hydroxides of Lanthanoids decreases from La(OH) 3 to Lu(OH) 3 . This is a consequence of: Lanthanoid contraction decreasing the size and increasing covalent character Increase in atomic number making the metal more electronegative Increase in the number of 4f electrons shielding the nucleus Decrease in the ionization enthalpy across the series Which of the following actinoids has the highest possible oxidation state of +7 ? Np and Pu U and Th Am and Cm Cf and Es The separation of Lanthanoid ions ( Ln 3+ ) by the ion-exchange method is primarily based on the difference in their: Hydrated ionic radii Electronegativity Standard reduction potential Mass number The maximum oxidation state shown by the actinoid element Americium ( Am, Z=95 ) is: +6 +7 +4 +3 Which of the following lanthanoid ions acts as a strong reducing agent in aqueous solution? Sm 2+ Ce 4+ Gd 3+ Lu 3+ Which of the following is NOT a consequence of lanthanoid contraction? The change in the magnetic properties of transition metals The difficulty in the separation of lanthanoids Similar atomic radii of Zr and Hf The decrease in basicity of hydroxides from La(OH) 3 to Lu(OH) 3 Europium ( Eu ) and Terbium ( Tb ) compounds are extensively used as phosphors in television and computer monitors because they: Emit strong red and green light respectively upon excitation Are cheap and abundantly available Conduct electricity better than other lanthanoids Have very high melting points and stability The common oxidation state of all lanthanoids is: +3 +2 +4 +5 Which lanthanoid element is known for its use in 'Sunlight-simulating' lamps? Cerium Thulium Erbium Lutetium The IE 1 of 5d series elements is generally higher than that of 4d series elements. This is due to: Greater effective nuclear charge because of Lanthanoid Contraction Decrease in atomic size in 4d series Inert pair effect Stability of half-filled subshells The most basic hydroxide among the following is: La(OH) 3 Gd(OH) 3 Eu(OH) 3 Lu(OH) 3 Identify the incorrect statement regarding the magnetic properties of lanthanoids. La 3+ and Lu 3+ are paramagnetic. Paramagnetism is maximum in the middle of the series ( Gd 3+ ). The magnetic moment of lanthanoids involves both spin and orbital angular momentum. Sharp absorption bands in their spectra are due to f-f transitions. The main reason for larger number of oxidation states exhibited by the actinoids than the corresponding lanthanoids, is :- Lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals More energy difference between 5f and 6d orbitals than between 4f and 5d orbitals Greater reactive nature of the actinoids than the lanthanoids Larger atomic size of actinoids than the lanthanoids Which of the following lanthanoid ions is diamagnetic? (At. nos. Ce = 58, Sm = 62, Eu = 63, Yb = 70) Ce 2+ Sm 2+ Eu 2+ Yb 2+ The electronic configurations of Eu(Atomic No 63), Gd(Atomic No 64) and Tb (Atomic No. 65) are [ Xe ]4f 7 6s 2 , [ Xe ]4f 8 6s 2 and [ Xe ]4f 8 5d 1 6s 2 [ Xe ]4f 7 5d 1 6s 2 , [ Xe ]4f 7 5d 1 6s 2 and [ Xe ]4f 9 6s 2 [ Xe ]4f 6 5d 1 6s 2 , [ Xe ]4f 7 5d 1 6s 2 and [ Xe ]4f 8 5d 1 6s 2 [ Xe ]4f 7 6s 2 , [ Xe ]4f 7 5d 1 6s 2 and [ Xe ]4f 9 6s 2 Which of the following lanthanoids shows +4 oxidation state to acquire noble gas configuration ? (At nos. : La = 57, Ce = 58, Eu = 63 and Yb = 70) Eu Ce Yb La The incorrect statement among the following is : Most of the trivalent Lanthanoid ions are colorless in the solid state Lanthanoids are good conductors of heat and electricity Actinoids are highly reactive metals, especially when finely divided. Actinoid contraction is greater for element to element than lanthanoid contraction Gadolinium has a low value of third ionisation enthalpy because of high exchange enthalpy high electronegativity high basic character small size Identify the element that does NOT belong to the 5f series (Actinoids). Terbium ( Tb ) Curium ( Cm ) Berkelium ( Bk ) Americium ( Am ) The pair of lanthanoid ions which are diamagnetic is Ce 4+ and Yb 2+ Ce 3+ and Eu 2+ Gd 3+ and Eu 3+ Pm 3+ and Sm 3+ Which of the following lanthanoid ions is diamagnetic? Yb 2+ Ce 2+ Sm 2+ Eu 2+ Which of the following statements about the chemistry of Lanthanoids is correct? All lanthanoids are much less reactive than aluminum Ln(III) compounds are generally colorless The basicity of hydroxides decreases with increase in atomic number Atomic radii of Zr and Hf are different The contraction in atomic and ionic radii in actinoids is greater than in lanthanoids because: 5f orbitals have poorer shielding effect than 4f orbitals 5f orbitals have better shielding effect than 4f orbitals 5f orbitals are closer to the nucleus Actinoids have more protons than lanthanoids Which of the following lanthanoid ions shows the maximum number of unpaired electrons? Gd 3+ Eu 2+ Tb 4+ All of these Which of the following properties of actinoids is fundamentally different from lanthanoids due to the poor shielding of 5f electrons? Greater ability to form complexes with -bonding ligands Similarity in chemical properties within the series Predominant +3 oxidation state Para-magnetic behavior of most ions Which of the following statements is TRUE regarding the magnetic properties of actinoids? Their magnetic moments are more complex to interpret than lanthanoids due to orbital contribution They are all diamagnetic The spin-only formula applies perfectly to all actinoid ions They have much lower magnetic moments than transition metals The actinoid used in the manufacture of gas mantles is: Thorium ( Th ) Uranium ( U ) Plutonium ( Pu ) Neptunium ( Np ) The absorption spectra of Lanthanoids exhibit very sharp bands. This is due to: f-f transitions being shielded by outer s and p orbitals Strong interaction with the ligands Large number of unpaired electrons in 5d orbitals High charge-to-radius ratio Identify the incorrect statement regarding the magnetic properties of actinoids. The magnetic properties of actinoids are easily explained by the spin-only formula. Most actinoid ions are paramagnetic. The magnetic susceptibility is lower for actinoids than for lanthanoids. Paramagnetism arises from the presence of unpaired 5f electrons. What is the correct order of decreasing ionic radii of the following trivalent lanthanoid ions? La 3+ > Ce 3+ > Pm 3+ > Yb 3+ Yb 3+ > Pm 3+ > Ce 3+ > La 3+ Ce 3+ > La 3+ > Pm 3+ > Yb 3+ Pm 3+ > La 3+ > Ce 3+ > Yb 3+ The electronic configuration of Thorium ( Th, Z=90 ) is unusual because it has: No electrons in the 5f subshell A completely filled 5f subshell Seven electrons in the 5f subshell No electrons in the 6d subshell The f-f transitions in lanthanoids result in sharp absorption bands because: The 4f orbitals are deeply buried and shielded by 5s and 5p electrons The 4f electrons are easily affected by the ligand field They are allowed transitions according to Selection Rules The 4f subshell is on the surface of the atom Which of the following lanthanoid ions is a powerful oxidizing agent, capable of oxidizing water, though the reaction is very slow? Pr 4+ Eu 2+ Yb 2+ La 3+ Compared to the d-d transitions in 3d series elements, the f-f transitions in lanthanoid ions result in: Sharper and narrower absorption bands Broad and intense absorption bands Bands in the Ultraviolet region only No absorption bands because they are forbidden In the separation of lanthanoid ions ( Ln 3+ ) by ion-exchange chromatography using a cation exchange resin, the ion that is eluted (comes out) last is: La 3+ Lu 3+ Gd 3+ Ce 3+ Which actinoid element has the most stable +2 oxidation state? Nobelium ( No ) Americium ( Am ) Thorium ( Th ) Uranium ( U ) The correct electronic configuration of Americium ( Z=95 ) is: [Rn]5f 7 7s 2 [Rn]5f 7 6d 1 7s 2 [Rn]5f 6 6d 1 7s 2 [Rn]5f 8 7s 1 Which of the following lanthanoid ions is used as a phosphor in fluorescent lamps to provide a red color? Eu 3+ Tb 3+ Ce 3+ Nd 3+ Which of the following electronic configurations represents the actinoid element Nobelium ( Z=102 )? [Rn] 5f 14 7s 2 [Rn] 5f 14 6d 1 7s 2 [Rn] 5f 13 7s 2 [Rn] 5f 14 6d 2 7s 2 The electronic configuration of Curium ( Z=96 ) is: [Rn] 5f 7 6d 1 7s 2 [Rn] 5f 8 7s 2 [Rn] 5f 7 6d 2 7s 1 [Rn] 5f 8 6d 1 7s 2 The oxidation state of U in [UO 2] 2+ is: +6 +4 +2 +5 Which lanthanoid element is used in goggles for glass blowers because it absorbs intense yellow light from sodium? Neodymium Cerium Europium Lutetium Which of the following statements about the f-f transitions in lanthanoids is true? They are Laporte forbidden, resulting in weak colors. They are Laporte allowed, resulting in intense colors. They occur in the ultraviolet region only. They are responsible for the magnetic properties only. Which of the following actinoids shows the oxidation state of +2? Americium Thorium Protactinium Neptunium The lanthanide ion having four unpaired electrons is (Given : Atomic numbers of Ce = 58, Nd = 60, Tb = 65 and Ho = 67) Nd 3+ Ce 3+ Tb 3+ Ho 3+ Mischmetal, widely used in cigarette lighters, contains primarily: Cerium and Iron Lanthanum and Copper Gadolinium and Gold Actinium and Iron Which of the following statements about the f -block elements is INCORRECT? All actinoids are non-radioactive Lanthanoids are collectively called rare earth elements The most common oxidation state for both series is +3 Actinoid contraction is more pronounced than lanthanoid contraction