Q.1 Which of the following elements is a Lanthanide?
Thorium (Th)
Uranium (U)
Neodymium (Nd)
Plutonium (Pu)
Explanation - Lanthanides are the 14 elements from La (57) to Lu (71). Neodymium (Nd) falls in this series.
Correct answer is: Neodymium (Nd)
Q.2 Which f-block element is commonly used in nuclear reactors as a fuel?
Uranium (U)
Cerium (Ce)
Lanthanum (La)
Gadolinium (Gd)
Explanation - Uranium-235, an actinide, is widely used as fuel in nuclear reactors due to its fissile properties.
Correct answer is: Uranium (U)
Q.3 Which property is characteristic of most Lanthanides?
Low melting points
High density
Non-metallic behavior
Low atomic number
Explanation - Lanthanides are dense metals with high melting points and metallic characteristics.
Correct answer is: High density
Q.4 Which actinide is commonly used in smoke detectors?
Thorium (Th)
Plutonium (Pu)
Americium (Am)
Neptunium (Np)
Explanation - Americium-241 is used in ionization smoke detectors due to its alpha-emitting properties.
Correct answer is: Americium (Am)
Q.5 The f-orbitals begin to fill in which period of the periodic table?
Period 4
Period 5
Period 6
Period 7
Explanation - The 4f orbitals (Lanthanides) begin to fill in period 6 of the periodic table.
Correct answer is: Period 6
Q.6 Which of the following elements exhibits +3 as its most stable oxidation state?
Lanthanum (La)
Thorium (Th)
Uranium (U)
Plutonium (Pu)
Explanation - Lanthanides commonly show a +3 oxidation state due to the loss of three outer electrons.
Correct answer is: Lanthanum (La)
Q.7 Which of the following is a radioactive actinide?
Cerium (Ce)
Uranium (U)
Neodymium (Nd)
Samarium (Sm)
Explanation - Actinides are mostly radioactive. Uranium is a naturally occurring radioactive actinide.
Correct answer is: Uranium (U)
Q.8 Which element is used as a catalyst in the hydrogenation of fats?
Lanthanum (La)
Cerium (Ce)
Plutonium (Pu)
Nickel (Ni)
Explanation - Trick question: Among f-block, cerium is used in redox reactions but not hydrogenation; the correct industrial hydrogenation catalyst is Nickel (Ni), not f-block.
Correct answer is: Nickel (Ni)
Q.9 Which f-block element is known for the phenomenon called 'lanthanide contraction'?
Lanthanum (La)
Neodymium (Nd)
Lutetium (Lu)
Thorium (Th)
Explanation - Lanthanide contraction refers to the gradual decrease in ionic radii from La to Lu due to poor shielding of 4f electrons.
Correct answer is: Lutetium (Lu)
Q.10 Which actinide is the heaviest naturally occurring element?
Uranium (U)
Thorium (Th)
Plutonium (Pu)
Neptunium (Np)
Explanation - Uranium (atomic number 92) is the heaviest naturally occurring actinide on Earth.
Correct answer is: Uranium (U)
Q.11 Which element is used in high-intensity carbon arc lamps?
Thorium (Th)
Lanthanum (La)
Cerium (Ce)
Uranium (U)
Explanation - Thorium oxide is used in carbon electrodes for high-intensity carbon arc lamps due to its high melting point.
Correct answer is: Thorium (Th)
Q.12 Which of the following is a typical property of actinides?
Non-radioactive
Highly electropositive
Low density
High electronegativity
Explanation - Actinides are metals with high electropositivity, reacting readily with non-metals.
Correct answer is: Highly electropositive
Q.13 Which of the following Lanthanides is most commonly used in strong permanent magnets?
Samarium (Sm)
Cerium (Ce)
Praseodymium (Pr)
Gadolinium (Gd)
Explanation - Samarium-cobalt magnets are strong permanent magnets widely used in electronics.
Correct answer is: Samarium (Sm)
Q.14 Which element is known for its use in control rods in nuclear reactors?
Thorium (Th)
Uranium (U)
Gadolinium (Gd)
Plutonium (Pu)
Explanation - Gadolinium has a high neutron absorption cross-section and is used in nuclear reactor control rods.
Correct answer is: Gadolinium (Gd)
Q.15 Which actinide is used in radiotherapy for cancer treatment?
Thorium (Th)
Americium (Am)
Uranium (U)
Plutonium (Pu)
Explanation - Americium-241 emits alpha particles and is used in targeted radiotherapy for certain cancers.
Correct answer is: Americium (Am)
Q.16 Which element shows a variable oxidation state from +3 to +6?
Thorium (Th)
Uranium (U)
Cerium (Ce)
Lanthanum (La)
Explanation - Uranium exhibits multiple oxidation states: +3, +4, +5, and +6 depending on chemical environment.
Correct answer is: Uranium (U)
Q.17 Which Lanthanide is used in color television tubes to produce red color?
Europium (Eu)
Gadolinium (Gd)
Neodymium (Nd)
Samarium (Sm)
Explanation - Europium compounds are used as red phosphors in color television and LED screens.
Correct answer is: Europium (Eu)
Q.18 Which property increases across the Lanthanide series despite constant oxidation state?
Ionic radius
Atomic radius
Density
Ionization energy
Explanation - Lanthanide contraction causes a gradual decrease in atomic and ionic radii, resulting in slightly increased ionization energy.
Correct answer is: Ionization energy
Q.19 Which actinide is commonly used as a target material for producing transuranic elements?
Thorium (Th)
Uranium (U)
Plutonium (Pu)
Neptunium (Np)
Explanation - Uranium-238 is bombarded with neutrons or other particles to produce transuranic elements in laboratories.
Correct answer is: Uranium (U)
Q.20 Which element is often used in phosphors for fluorescent lamps?
Lanthanum (La)
Cerium (Ce)
Thorium (Th)
Plutonium (Pu)
Explanation - Cerium-doped phosphors emit visible light when excited by ultraviolet light in fluorescent lamps.
Correct answer is: Cerium (Ce)
Q.21 Which of the following is a light Lanthanide?
Lanthanum (La)
Ytterbium (Yb)
Lutetium (Lu)
Thulium (Tm)
Explanation - Light Lanthanides are La to Sm, heavier ones are from Eu to Lu.
Correct answer is: Lanthanum (La)
Q.22 Which actinide is used in the production of nuclear weapons?
Thorium (Th)
Plutonium (Pu)
Americium (Am)
Uranium (U)
Explanation - Plutonium-239 is a fissile material used in nuclear weapons.
Correct answer is: Plutonium (Pu)
Q.23 Which element is known to have the highest melting point among Lanthanides?
Lanthanum (La)
Gadolinium (Gd)
Lutetium (Lu)
Neodymium (Nd)
Explanation - Gadolinium has the highest melting point (~1312°C) among Lanthanides.
Correct answer is: Gadolinium (Gd)
Q.24 Which of the following is a synthetic actinide?
Uranium (U)
Plutonium (Pu)
Thorium (Th)
Neptunium (Np)
Explanation - Plutonium is mostly synthetic, produced by neutron irradiation of Uranium-238.
Correct answer is: Plutonium (Pu)
Q.25 Which Lanthanide is used as a catalyst in catalytic converters of automobiles?
Cerium (Ce)
Lanthanum (La)
Europium (Eu)
Samarium (Sm)
Explanation - Cerium oxide is used in catalytic converters to oxidize CO to CO2, improving emission control.
Correct answer is: Cerium (Ce)