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A. Partially filled d-orbitals in the atom or a common oxidation state
B. Fully filled d-orbitals only
C. Completely empty d-orbitals
D. Partially filled f-orbitals
Answer: A. Partially filled d-orbitals in the atom or a common oxidation state
Explanation: Transition elements have partially filled d-subshells in their atomic or ionic states.
2. Which of the following is a characteristic property of transition metals?
A. Variable oxidation states
B. A single fixed oxidation state
C. Non-metallic character
D. Generally low melting points
Answer: A. Variable oxidation states
Explanation: Transition metals commonly show multiple oxidation states because both ns and (n-1)d electrons can be involved in bonding.
3. Lanthanoid contraction refers to the:
A. Steady decrease in atomic and ionic radii across the lanthanoid series
B. Steady increase in radii across the series
C. No change in radii across the series
D. Sudden decrease followed by an increase
Answer: A. Steady decrease in atomic and ionic radii across the lanthanoid series
Explanation: Poor shielding by 4f electrons causes a gradual, cumulative decrease in size across the lanthanoid series.
4. Transition metals show good catalytic activity mainly due to:
A. Their variable oxidation states and large surface area
B. Their high melting points
C. Their characteristic colour
D. Their magnetic nature
Answer: A. Their variable oxidation states and large surface area
Explanation: Variable oxidation states allow transition metals to form intermediates easily, while their large surface area provides adsorption sites for reactants.
5. Which transition metal ion is colourless due to its d10 configuration?
A. Zn²⁺
B. Cu²⁺
C. Fe²⁺
D. Mn²⁺
Answer: A. Zn²⁺
Explanation: With a completely filled d10 configuration, Zn²⁺ cannot undergo d-d electronic transitions, so it appears colourless.
6. KMnO4 acts as a strong oxidizing agent because manganese is present in the:
A. +7 oxidation state
B. +2 oxidation state
C. 0 oxidation state
D. +4 oxidation state
Answer: A. +7 oxidation state
Explanation: In KMnO4, manganese is in its highest common oxidation state (+7), giving it a strong tendency to be reduced, hence strong oxidizing power.
7. Actinoid contraction is generally greater than lanthanoid contraction because of:
A. Poorer shielding by 5f electrons compared to 4f electrons
B. Better shielding by 5f electrons
C. A larger decrease in nuclear charge
D. The complete absence of 5f electrons
Answer: A. Poorer shielding by 5f electrons compared to 4f electrons
Explanation: 5f orbitals shield the nuclear charge less effectively than 4f orbitals, leading to a greater contraction across the actinoid series.
8. Interstitial compounds of transition metals are formed when small atoms such as H, C, or N occupy:
A. Interstitial voids in the metal lattice
B. Substitutional lattice sites only
C. The outermost electron shell
D. Positions outside the crystal lattice
Answer: A. Interstitial voids in the metal lattice
Explanation: Small non-metal atoms like hydrogen, carbon, and nitrogen fit into the empty spaces (interstitial voids) within the metal crystal lattice.
9. Which of the following compounds is commonly used as a strong oxidizing agent in acidic medium?
A. K2Cr2O7
B. NaCl
C. CaCO3
D. KCl
Answer: A. K2Cr2O7
Explanation: Potassium dichromate (K2Cr2O7) is a well-known strong oxidizing agent in acidic solution, being reduced from Cr(VI) to Cr(III).
10. Transition metal compounds are frequently coloured mainly due to:
A. d-d electronic transitions
B. s-s electronic transitions
C. p-p electronic transitions
D. The complete absence of electronic transitions
Answer: A. d-d electronic transitions
Explanation: Absorption of visible light promotes electrons between split d-orbitals (d-d transitions), giving rise to characteristic colours.
11. The most common and stable oxidation state shown by lanthanoids is:
A. +3
B. +2
C. +4
D. +1
Answer: A. +3
Explanation: Lanthanoids predominantly exhibit the +3 oxidation state, corresponding to loss of the two 6s and one 5d/4f electron.
12. Which of the following is generally NOT classified as a typical transition element?
A. Zn
B. Fe
C. Cu
D. Mn
Answer: A. Zn
Explanation: Zinc has a completely filled 3d10 configuration in its elemental and common ionic (Zn²⁺) forms, so it is usually excluded from typical transition elements.
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