NCERT Solutions for Class 12 Chemistry Chapter 4 The d and f Block Elements - Free PDF Download
Chapter 4 Chemistry Class 12 deals with the d and f block of the modern periodic table. The chapter is essential to understand the electronic configuration and the general characteristics of transition elements, oxidization, and chemical reactivity.
For students appearing in the board exams, this chapter is crucial as several essential questions are set from this chapter. In this regard, the Class 12 Chemistry Chapter 4 NCERT solutions come as a great help.
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Important Topics Covered in NCERT Solutions Class 12 Chemistry Chapter 4 The d- and f-block Elements
Students are suggested to go through the following topics and the subsequent sub-topics from NCERT Class 12 Chemistry Chapter 4 thoroughly for their exam preparation.
Position of d-block Elements in the Periodic Table
Position of f-block Elements in the Periodic Table
Electronic Configuration of d-block Elements
General Properties of the d-block Elements or Transition Elements
Transition Elements Important Compounds
Lanthanoids and Actinoids
Applications of d and f-block Elements
The d-and f-Block Elements Chapter at a Glance - Class 12 NCERT Solutions
d-Block Elements
d-block elements are those in which the last electron goes to (n-1) d-orbitals.
General electronic configurations of d-block elements is : ns1-2, (n-1)d1-10
Transition metals have high values of melting and boiling points which are due to the presence of strong metallic bonding in these metals.
Due to lanthanide contraction, atomic radii for the elements of 3rd transition series are almost equal to those for the elements of 2nd transition series.
The values of ionisation energies increase as we move from left to right in each series.
Except for Cu, E°red values for other metals of 1st transition series are negative.
Excepting a few metals, most of the metals show several oxidation states. This is due to the fact that (n-1)d and ns orbitals have almost the same energy.
Transition metal ions which contain partially filled d-orbitals are usually coloured. The colour arises because of d0-d10 transition. Transition metal ions with d0 or d10 configuration
are colourless because d-d transition is not possible in such ions.
Transition metals form interstitial compounds.
Many transition metals and their alloys and compounds act as catalysts in many chemical reactions.
f-Block Elements
The elements in which the last electron enters f-orbital of (n- 2)th shell are called f-block elements. f-block elements are of two types lanthanides and actinides.
General electronic configuration of f-block elements is ns2, (n-1)d0-1, (n-2)f1-14
+ 3 oxidation state (O.S.) is the most stable O.S. of lanthanides.
There is a steady decrease in atomic and ionic (M3+ ions) radii of lanthanides. This steady decrease in atomic and ionic radii is called lanthanide contraction.
Magnetic moment value of lanthanides and actinides is calculated by considering both orbital spin contribution. Μeff value is given by μeff = 4S (S+1)+L(L+1) B.M, here S spin quantum number and L= orbital quantum number
Mischmetal is an important alloy of lanthanides. It contains 90% lanthanides (La= 40%, Ce and other lanthanides= 50%) , Fe = 5% and traces of other elements like C, S, Al, Ca.
The actinide elements lying beyond U (Np-93 to Lw-103) are called trans-uranic or trans-uranium elements.
Unlike lanthanides, actinides show a large number of oxidation states.
Actinides have lower values of ionisation energies.
Most of actinide halides form complex compounds with alkali metal halides. The degree of complex formation for the ions decreases as : M4+ > MO2 2+ > M3+ > MO2+.
Thorium is used in atomic reactors and in the treatment of cancer. Uranium is used as a nuclear fuel. Plutonium is used as a fuel for atomic reactors as well as for making atomic bombs.
d-and f-Block Elements
FAQs on NCERT Solutions for Class 12 Chemistry Chapter 4 The D and F Block Elements
1. What is the step-by-step method to solve electronic configuration questions in NCERT Solutions for Class 12 Chemistry Chapter 4?
To solve electronic configuration questions, first identify the atomic number of the element, determine its period and block in the periodic table, and write the configuration using the Aufbau principle. Then, fill electrons into orbitals in order of increasing energy and double-check the final placement for anomalies such as exceptions found in chromium or copper. Use ns and (n-1)d notations as guided by CBSE for d-block elements.
2. How should students approach stepwise explanations for variable oxidation states in transition metals using NCERT Solutions?
Begin by writing the complete electronic configuration of the metal atom. Identify the possible oxidation states by removing electrons from the ns and then (n-1)d orbitals. For each step, check stability based on electron pairing and the presence of half-filled or fully filled d-subshells, as emphasized in NCERT Solutions for Class 12 Chemistry Chapter 4. State the reasoning why certain states are more common, such as +2 and +3 in iron.
3. What is the method to justify the color of transition metal compounds according to the NCERT Solutions for The d and f Block Elements?
Apply the concept of d-d electronic transitions. After writing the configuration of the metal ion in the compound, determine if d-orbitals are partially filled. If they are, explain that the absorption of visible light allows electrons to jump between split d-levels, resulting in color. Solutions should clarify that ions with d0 or d10 configurations are colorless.
4. How do the NCERT Solutions explain the stepwise calculation of magnetic moment for lanthanides and actinides?
Start by determining the number of unpaired electrons and the values of the spin quantum number (S) and orbital quantum number (L). Use the formula μeff = √[4S(S+1) + L(L+1)] BM as given in the chapter. Substitute the appropriate values for S and L based on the electron configuration, then calculate the result in Bohr magnetons for the specific lanthanide or actinide ion.
5. What are common pitfalls students should avoid when solving NCERT Solutions for the d and f Block Elements?
Avoid misplacing electrons in electronic configurations, particularly for exceptions (e.g., chromium, copper). Do not assume all transition metals show similar oxidation states; check each case. Thoroughly read questions to note if the compound asked is for an atom or ion. Pay attention to wording in CBSE pattern questions which may require explanations with examples or supporting diagrams.
6. Why is stepwise problem-solving recommended in NCERT Solutions for Class 12 Chemistry Chapter 4?
Stepwise problem-solving helps in breaking down complex concepts, minimizing errors, and improving answer clarity as required in CBSE exams. Each step ensures logical progression, supporting answers with diagrams or configurations, which is essential for scoring full marks according to NCERT guidelines.
7. How do NCERT Solutions for Chapter 4 help distinguish between transition and inner transition elements?
They emphasize the basis of differentiation as the presence of partially filled d-orbitals for transition elements (d-block) and partially filled f-orbitals for inner transition elements (f-block). Electronic configuration and their location in the periodic table are used in stepwise exercises to reinforce this distinction, directly aligning with CBSE exam requirements.
8. What advanced steps are taken in NCERT Solutions to clarify the concept of lanthanide contraction and its consequences?
NCERT Solutions include detailed comparison of ionic radii as atomic number increases and relate this steady decrease to poor shielding by f-electrons. The solutions then guide students to link lanthanide contraction to chemical properties such as similarity in radii between 2nd and 3rd transition series, differences in complex formation, and variations in basicity, encouraging application-level reasoning.
9. How do NCERT Solutions connect theory with application in questions on industrial uses of d and f block elements?
Solutions require students to match specific properties from theory (e.g., variable oxidation states, catalytic abilities) to relevant real-world uses:
- Transition metals as catalysts in industrial processes like ammonia synthesis
- Lanthanoids in alloy manufacturing and electronic devices
- Actinoids for nuclear fuel and medical applications
10. What are effective revision strategies provided by NCERT Solutions for scoring well in Chapter 4 The d and f Block Elements?
Revise by
- Solving each exercise stepwise as demonstrated in solutions
- Focusing on diagrams, tables, and examples included
- Practicing past CBSE-style conceptual and reason-based questions
- Clarifying misconceptions using detailed step explanations
