Questions on Lanthanides and Actinides
Multiple-Choice Questions: Lanthanides and Actinides
🔹 Lanthanides & Actinides: Basic Properties
1. Lanthanides belong to which block of the periodic table?
A) s-block
B) p-block
C) d-block
D) f-block
E) g-block
2. Actinides are known for being:
A) Highly stable and non-radioactive
B) Mostly synthetic and radioactive
C) Non-metals
D) Noble gases
E) Halogens
3. Which element is the first lanthanide?
A) Cerium (Ce)
B) Lanthanum (La)
C) Neodymium (Nd)
D) Samarium (Sm)
E) Europium (Eu)
4. Which element is the first actinide?
A) Uranium (U)
B) Plutonium (Pu)
C) Thorium (Th)
D) Actinium (Ac)
E) Neptunium (Np)
5. The electron configuration of lanthanides typically involves filling of which orbitals?
A) 4f orbitals
B) 3d orbitals
C) 5d orbitals
D) 6s orbitals
E) 2p orbitals
🔹 Physical and Chemical Properties
6. Lanthanides are known for having:
A) Low melting points
B) High magnetic susceptibility
C) No metallic character
D) Inertness to acids
E) Being gases at room temperature
7. Actinides are typically:
A) All naturally occurring
B) All radioactive
C) Non-metals
D) Halogens
E) Inert gases
8. Which of the following lanthanides is commonly used in strong permanent magnets?
A) Cerium
B) Neodymium
C) Lanthanum
D) Europium
E) Gadolinium
9. What is the common oxidation state exhibited by most lanthanides?
A) +1
B) +2
C) +3
D) +4
E) +5
10. Which actinide is commonly used as nuclear fuel in reactors?
A) Thorium
B) Uranium
C) Plutonium
D) Actinium
E) Californium
🔹 Radioactivity and Applications
11. Which of these actinides is synthetic and used in nuclear weapons?
A) Thorium
B) Uranium
C) Plutonium
D) Neptunium
E) Protactinium
12. The “lanthanide contraction” refers to:
A) The increasing atomic radius across the series
B) The decrease in atomic radius despite increasing atomic number
C) The expansion of the nucleus
D) The contraction of the electron cloud in the p-block
E) The increase in ionization energy in alkali metals
13. Which lanthanide is used in the production of color television screens?
A) Europium
B) Samarium
C) Dysprosium
D) Terbium
E) Gadolinium
14. Most actinides have:
A) Stable isotopes
B) Only one common oxidation state
C) Multiple oxidation states and radioactivity
D) Low densities
E) No practical applications
15. Which actinide has the highest atomic number found naturally on Earth?
A) Uranium
B) Plutonium
C) Neptunium
D) Thorium
E) Protactinium
🔹 Chemical Reactivity & Compounds
16. Lanthanides tend to form compounds primarily with which oxidation state?
A) +2
B) +3
C) +4
D) +5
E) +6
17. Which element is often considered the "gateway" between transition metals and lanthanides?
A) Scandium
B) Yttrium
C) Lanthanum
D) Actinium
E) Cerium
18. Actinides typically form compounds with:
A) Nonmetals only
B) Metals only
C) Both metals and nonmetals
D) Noble gases
E) Alkali metals only
19. Which of the following lanthanides is used as a phosphor in lighting?
A) Ytterbium
B) Terbium
C) Lutetium
D) Cerium
E) Promethium
20. Which actinide element is used in smoke detectors?
A) Uranium
B) Thorium
C) Americium
D) Curium
E) Californium
🔹 Environmental & Health Aspects
21. Which lanthanide has no stable isotopes and is therefore radioactive?
A) Promethium
B) Samarium
C) Dysprosium
D) Terbium
E) Europium
22. Which actinide is considered the most abundant in the Earth's crust?
A) Uranium
B) Thorium
C) Plutonium
D) Neptunium
E) Americium
23. Exposure to which actinide poses the greatest radiological hazard?
A) Uranium
B) Thorium
C) Plutonium
D) Actinium
E) Californium
24. Lanthanides are primarily extracted from:
A) Coal deposits
B) Bauxite ore
C) Rare earth minerals
D) Oil shale
E) Iron ore
25. Which actinide is used in neutron sources for scientific instruments?
A) Californium
B) Thorium
C) Uranium
D) Plutonium
E) Neptunium
🔹 Advanced Chemistry & Trends
26. The color of many lanthanide compounds is:
A) Very bright and varied due to 4f-4f transitions
B) Colorless because f-orbitals do not participate in bonding
C) Uniformly black
D) The same as transition metals
E) Due to s-p transitions
27. Which of the following best explains the actinide contraction?
A) Increased shielding by 5f electrons
B) Poor shielding by 5f electrons leading to contraction
C) Shielding by 6d electrons
D) Expansion due to extra protons
E) None of the above
28. Which lanthanide is considered the most abundant in the Earth’s crust?
A) Neodymium
B) Cerium
C) Lanthanum
D) Gadolinium
E) Europium
29. Which actinide is used as a fuel in some nuclear reactors as an alternative to uranium?
A) Thorium
B) Plutonium
C) Americium
D) Curium
E) Californium
30. The major challenge in separating lanthanides from each other is:
A) Their widely differing chemical properties
B) Their very similar ionic radii and chemical behavior
C) Their radioactive nature
D) Their gaseous state
E) Their instability
- Questions on Alkaline Earth Metals (Group 2)
- Questions on Halogens (Group 17 Elements)
- Questions on Transition Metals (d-block elements)
Answers with Extended Explanations
1. D – f-block
→ Lanthanides fill the 4f orbitals and belong to the f-block.
2. B – Mostly synthetic and radioactive
→ Actinides include both natural and synthetic elements; many are radioactive.
3. B – Lanthanum (La)
→ Lanthanum starts the lanthanide series but technically is not a lanthanide by some definitions; it precedes the 4f filling.
4. D – Actinium (Ac)
→ Actinium is the first actinide element.
5. A – 4f orbitals
→ Lanthanides primarily fill 4f orbitals.
6. B – High magnetic susceptibility
→ Lanthanides are strongly paramagnetic due to unpaired 4f electrons.
7. B – Neodymium
→ Neodymium is used in powerful permanent magnets.
8. C – +3
→ +3 is the most common and stable oxidation state for lanthanides.
9. B – Uranium
→ Uranium is the primary fuel in nuclear reactors.
10. C – Plutonium
→ Plutonium-239 is used in nuclear weapons and reactors.
11. B – The decrease in atomic radius despite increasing atomic number
→ Lanthanide contraction refers to the unexpected decrease in atomic size.
12. A – Europium
→ Europium phosphors are used in red/blue coloring for displays.
13. C – Multiple oxidation states and radioactivity
→ Actinides are chemically complex and radioactive.
14. A – Uranium
→ Uranium is the heaviest naturally occurring actinide.
15. B – +3
→ Lanthanides mostly show +3 oxidation states in their compounds.
16. C – Lanthanum
→ Lanthanum bridges transition metals and lanthanides.
17. C – Both metals and nonmetals
→ Actinides form various compounds with both.
18. B – Terbium
→ Terbium is used in phosphors for green lighting.
19. C – Americium
→ Americium-241 is used in smoke detectors.
20. A – Promethium
→ Promethium is radioactive and has no stable isotopes.
21. B – Thorium
→ Thorium is the most abundant actinide in the Earth’s crust.
22. C – Plutonium
→ Plutonium is highly radiotoxic and poses health risks.
23. C – Rare earth minerals
→ Lanthanides are extracted primarily from minerals like monazite and bastnäsite.
24. A – Californium
→ Californium is used as a neutron source.
25. A – Very bright and varied due to 4f-4f transitions
→ Lanthanide ions show sharp emission lines due to 4f electrons.
26. B – Poor shielding by 5f electrons leading to contraction
→ 5f electrons shield poorly, causing actinide contraction.
27. B – Cerium
→ Cerium is the most abundant lanthanide in the Earth's crust.
28. A – Thorium
→ Thorium can be used as a nuclear fuel alternative to uranium.
29. B – Their very similar ionic radii and chemical behavior
→ Lanthanides are hard to separate due to very similar chemical properties.
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