Which of the following statements about the oxidation states of transition metals is incorrect?

Transition metals only exhibit oxidation states that differ by two units.

Transition metals can exhibit multiple oxidation states.

The highest oxidation states are often stabilized in oxides and fluorides.

Transition metals only exhibit oxidation states that differ by two units.

Low oxidation states are stabilized by $c$-acceptor ligands.

Which of the following statements correctly explains why $Zn$, $Cd$, and $Hg$ are not considered true transition metals?

They have a completely filled $d^{10}$ configuration in their ground state and common oxidation states.

They have an incomplete $d$ subshell in their atoms or common ions.

They do not form colored compounds.

Why is the standard electrode potential $E^\circ$ for the $Cu^{2+}/Cu$ couple positive?

High atomisation enthalpy of $Cu$

High hydration enthalpy of $Cu^{2+}$

High atomisation enthalpy of $Cu$

Low ionisation enthalpy of $Cu$

High reduction potential of $Cu^{2+}$

Why do transition metals generally exhibit a decrease in atomic and ionic radii across a series?

Due to the increasing nuclear charge and poor shielding effect of d electrons.

Because of the filling of s orbitals which have a strong shielding effect.

The d orbitals are completely filled, preventing any change in atomic size.

The increase in the number of electron shells compensates for the nuclear charge.

Which of the following statements correctly differentiates between lanthanoids and actinoids?

Lanthanoids primarily exhibit the +3 oxidation state, while actinoids show a wider range of oxidation states.

Actinoids are less reactive than lanthanoids.

Lanthanoids have more complex chemistry than actinoids.

Actinoids have smoother trends in their properties compared to lanthanoids.

Why do transition metals generally have high melting points?

Due to the involvement of ns and (n-1)d electrons in metallic bonding

Because they have low atomic masses

Due to the presence of filled d orbitals

Why is $Cr^{2+}$ considered a reducing agent while $Mn^{3+}$ is considered an oxidizing agent, despite both having a $d^4$ configuration?

$Cr^{2+}$ changes to a more stable $d^3$ configuration.

$Mn^{3+}$ changes to a more stable $d^5$ configuration.

$Cr^{2+}$ loses an electron to achieve a half-filled $t_{2g}$ level.

Home

School

CBSE

Class 12 Science (PCB)

Chemistry Part 1

The d- and f-Block Elements

Learning Objectives

Top

Understand the positions of the d- and f-block elements in the periodic table.
Learn the electronic configurations of transition (d-block) and inner transition (f-block) elements.
Appreciate the relative stability of various oxidation states in terms of electrode potential values.
Describe the preparation, properties, structures, and uses of important compounds such as K₂Cr₂O₇ and KMnO₄.
Understand the general characteristics of the d- and f-block elements and the trends in their properties.

Practice, Analyze & Improve 🚀

Dont just read—test your knowledge! Unlock the Student Workspace to take chapter tests and get instant performance insights.

Deep Analytics

Peer Comparison

Track Progress

Claim Free Account100% Free • No credit card required

Revision Notes & Summary

Top

Notes on d- and f- Block Elements

1. Introduction to Transition Elements

The d-block consists of groups 3-12 in the periodic table.
Transition metals have partially filled d orbitals.
Common transition metals include iron, copper, silver, and gold.

2. Electronic Configurations

General electronic configuration: (n-1)d¹⁰ns¹⁻².
Exceptions:
- Chromium (Cr): 3d⁵ 4s¹ instead of 3d⁴ 4s².
- Copper (Cu): 3d¹⁰ 4s¹ instead of 3d⁹ 4s².

3. Oxidation States

Transition metals exhibit multiple oxidation states due to the involvement of d electrons.
Common oxidation states include +2, +3, and higher.

4. Properties of Transition Metals

Paramagnetism: Many transition metals and their compounds show paramagnetic behavior due to unpaired electrons.
Catalytic Activity: Transition metals often act as catalysts in various chemical reactions.
Color: Transition metal compounds are typically colored due to d-d electron transitions.

5. Inner Transition Elements

Comprises lanthanoids and actinoids.
Lanthanoids: Elements following lanthanum (atomic numbers 57-71).
Actinoids: Elements following actinium (atomic numbers 89-103).
Actinoids exhibit a wider range of oxidation states and are often radioactive.

6. Preparation of Compounds

Potassium Dichromate (K₂Cr₂O₇): Prepared from chromite ore.
Potassium Permanganate (KMnO₄): Prepared from pyrolusite ore.

7. Reactions Involving Potassium Permanganate

Oxidation reactions in acidic solutions:
- Oxalic acid: 5C₂O₄²⁻ + 2MnO₄ + 16H⁺ → 2Mn²⁺ + 8H₂O + 10CO₂
- Hydrogen sulfide: H₂S + 2MnO₄ + 16H⁺ → 2Mn²⁺ + 8H₂O + 5S

8. Disproportionation Reactions

Definition: A reaction where a substance is simultaneously oxidized and reduced.
Example: Cu⁺ undergoes disproportionation to form Cu²⁺ and Cu.

9. Stability of Oxidation States

Mn²⁺ compounds are more stable than Fe²⁺ towards oxidation to their +3 state due to electronic configuration stability.

10. Characteristics of Lanthanoids vs. Actinoids

Lanthanoids: Generally exhibit +3 oxidation state, less complex chemistry.
Actinoids: Exhibit multiple oxidation states, more complex due to radioactivity.

11. Summary of Key Points

Transition metals are defined by their d orbital configurations and exhibit unique properties.
Inner transition metals have distinct characteristics and complexities in their chemistry.

Do you belong in the Top 10%?

Our analytics show that most students struggle with specific concepts in The d- and f-Block Elements. Take a free diagnostic test to generate your personal Learning DNA profile.

Practice Test – MCQs, True/False

Top

Multiple Choice Questions

Fe^{3+}

Mn^{2+}

Co^{2+}

Ni^{2+}

Correct Answer: B

Solution:

Mn^{2+}

ions in aqueous solution exhibit a pink color due to their

3d^5

electronic configuration.

Chapter Concept:

Formation of Coloured Ions

^{3+}

^{3+}

^{2+}

^{3+}

Correct Answer: A

Solution:

^{3+}

has an electronic configuration of

3d^0

, meaning it has no unpaired electrons, resulting in a colorless solution.

Chapter Concept:

Magnetic Properties of Transition Metals

Experience the StudyTunnel Method

We do not just give you mock tests. We guide you through a gamified, AI-driven learning path designed to guarantee mastery.

Step 1: Practicing the Concepts

The d- and f-Block Elements

Step 2: Master Boss Exam

Locked • Full Phase Assessment

Step 3: Redemption Arena

Locked • AI Weakness Tracker

True or False

Correct Answer: True

Solution:

Transition metals have small ionic sizes, high ionic charges, and available

d

orbitals, which facilitate the formation of complex compounds.

Chapter Concept :

Formation and Stability of Complex Compounds

Correct Answer: True

Solution:

The spin-only magnetic moment is calculated using the formula

\mu = \sqrt{n(n+2)}

, where

n

is the number of unpaired electrons. For 3 unpaired electrons,

\mu = \sqrt{3(3+2)} = \sqrt{15} \approx 3.87

Bohr magnetons.

Chapter Concept :

Magnetic Properties of Transition Metals

Correct Answer: True

Solution:

Transition metal ions exhibit color due to the absorption of visible light, which causes d-d transitions between split d orbitals. The observed color is complementary to the absorbed color and depends on the nature of the ligand.

AI Learning Assistant

StudyTunnel Methodology

1

Master the Concepts

2

Conquer Boss Exams

3

The Redemption Arena

The d- and f-Block Elements

Learning Objectives

Practice, Analyze & Improve 🚀

Revision Notes & Summary

Notes on d- and f- Block Elements

1. Introduction to Transition Elements

2. Electronic Configurations

3. Oxidation States

4. Properties of Transition Metals

5. Inner Transition Elements

6. Preparation of Compounds

7. Reactions Involving Potassium Permanganate

8. Disproportionation Reactions

9. Stability of Oxidation States

10. Characteristics of Lanthanoids vs. Actinoids

11. Summary of Key Points

Do you belong in the Top 10%?

Practice Test – MCQs, True/False

Multiple Choice Questions

Q1.Which transition metal ion exhibits a pink color in aqueous solution?

Correct Answer: B

Q2.Which transition metal ion is most likely to be colorless in aqueous solution due to the absence of unpaired electrons?

Correct Answer: A

Experience the StudyTunnel Method

Step 1: Practicing the Concepts

Step 2: Master Boss Exam

Step 3: Redemption Arena

True or False

Q1.Transition metals form many complexes due to their small ionic size, high ionic charge, and availability of ddd orbitals for bonding.

Correct Answer: True

Q2.The spin-only magnetic moment for a transition metal ion with 3 unpaired electrons is approximately 3.87 Bohr magnetons.

Correct Answer: True

Q3.Transition metal ions are colored because d electrons absorb visible light and undergo d-d transitions between split d orbitals.

Correct Answer: True

Q3.Which of the following statements about the oxidation states of transition metals is incorrect?

Correct Answer: C

Unlock the Detailed Solution

Q4.Which of the following statements correctly explains why ZnZnZn, CdCdCd, and HgHgHg are not considered true transition metals?

Correct Answer: A

Unlock the Detailed Solution

Q5.Why is the standard electrode potential E∘E^\circE∘ for the Cu2+/CuCu^{2+}/CuCu2+/Cu couple positive?

Correct Answer: B

Unlock the Detailed Solution

Q6.Why do transition metals generally exhibit a decrease in atomic and ionic radii across a series?

Correct Answer: A

Unlock the Detailed Solution

Q7.Which of the following statements correctly differentiates between lanthanoids and actinoids?

Correct Answer: A

Unlock the Detailed Solution

Q8.Why do transition metals generally have high melting points?

Correct Answer: A

Unlock the Detailed Solution

Q9.Why is Cr2+Cr^{2+}Cr2+ considered a reducing agent while Mn3+Mn^{3+}Mn3+ is considered an oxidizing agent, despite both having a d4d^4d4 configuration?

Correct Answer: D

Unlock the Detailed Solution

Q10.Which lanthanoid ion is known for its stability due to a half-filled f subshell?

Correct Answer: B

Unlock the Detailed Solution

Sign in to reveal the answer

Q4.The electronic configuration of CuCuCu is 3d104s13d^{10}4s^13d104s1 instead of 3d94s23d^9 4s^23d94s2 due to the stability of a fully filled 3d3d3d subshell.

Correct Answer: True

Sign in to reveal the answer

Q5.Transition metals often exhibit oxidation states that differ by one unit.

Correct Answer: True

Sign in to reveal the answer

Q6.Transition metals can exhibit a variety of oxidation states due to the comparable energies of the nsnsns and (n−1)d(n-1)d(n−1)d electrons.

Correct Answer: True

Sign in to reveal the answer

Q7.Transition metal oxides can exhibit basic, amphoteric, or acidic properties depending on their oxidation state.

Correct Answer: True

Sign in to reveal the answer

Q8.Transition metal oxides with higher oxidation states are generally acidic.