D And F Block Elements

Step 1: Ti has the electron configuration [Ar] 3d , with two electrons in the 3d orbitals. In the presence of ligands (e.g., in salts), the d-orbitals split into lower-energy t and higher-energy e levels due to crystal field splitting. Electrons can transition between these levels (d-d transitions), absorbing visible light and causing the salts to appear coloured.
Step 2: For the divalent cation of the transition metal with atomic number 25 (Mn), the Mn ion has the configuration [Ar] 3d . This half-filled d configuration also allows d-d transitions in the ligand field, leading to absorption of visible light and coloured salts (e.g., pale pink in MnSO ).

Step 1: Lanthanoid Contraction: The lanthanoid contraction refers to the steady decrease in atomic and ionic radii of the lanthanoid elements (atomic numbers 58 to 71) as the atomic number increases. This occurs due to poor shielding of the 4f electrons, which causes the nuclear charge to pull the outer electrons closer, reducing the size.
Step 2: Preparation of Acetic Acid from Dry Ice: Dry ice (solid CO ) reacts with a Grignard reagent (methyl magnesium chloride, CH MgCl):
Step 3: Preparation of Acetic Acid from Ethyl Chloride: Ethyl chloride (C H Cl) is converted to a nitrile, then hydrolyzed:

The maximum oxidation state of a transition element often corresponds to the total number of valence electrons (s and d).
- Sc (3d 4s ): +3
- Fe (3d 4s ): +6 (in ferrates)
- Mn (3d 4s ): +7 (in permanganates, e.g., KMnO )
- V (3d 4s ): +5
Mn shows the highest oxidation state.
Answer: Mn.

Lanthanides and actinides are f-block elements, but they differ as follows:
1. **Electronic Configuration:**
- Lanthanides: Electrons fill the 4f orbitals ([Xe] 4f 5d 6s ).
- Actinides: Electrons fill the 5f orbitals ([Rn] 5f 6d 7s ).
2. **Radioactivity:**
- Lanthanides: Mostly non-radioactive (except promethium).
- Actinides: All are radioactive due to unstable nuclei.
3. **Oxidation States:**
- Lanthanides: Predominantly +3, rarely +2 or +4.
- Actinides: Show variable oxidation states (e.g., +3 to +6 for uranium).
4. **Chemical Reactivity:**
- Lanthanides: Less reactive, similar to group 2 metals.
- Actinides: More reactive, form complexes easily due to higher charge density.

Spin-Only Magnetic Moment Calculation
Step 1: Identify the element and its ion.
The element M with atomic number Z = 26 is Iron (Fe). We need to find the magnetic moment for the M ion, which is Fe .

Step 2: Write the electronic configurations.
Fe (Z=26): [Ar] 3d 4s
Fe : [Ar] 3d

Step 3: Determine the number of unpaired electrons (n).
In the 3d configuration, the electrons are distributed among the five d-orbitals. Following Hund's rule, there will be one pair and four unpaired electrons. So, n = 4.


Step 4: Calculate the magnetic moment ( ).
The formula for spin-only magnetic moment is Bohr Magnetons (BM).

Condensed Electronic Configuration of Gadolinium Gadolinium (Gd) has an atomic number Z = 64. Its configuration is an exception to the Aufbau principle due to the stability of the half-filled 4f subshell.
The condensed electronic configuration is:

Step 1: Understanding the Concept:
Lanthanoids (4f series) and Actinoids (5f series) are inner transition elements placed at the bottom of the periodic table.
Step 2: Detailed Explanation:
Similarities:
1. In both series, the last electron enters the f-orbital of the anti-penultimate shell ( ).
2. Both show a common and stable oxidation state of +3.
3. Both show a regular decrease in atomic and ionic radii with increasing atomic number (Lanthanoid and Actinoid contraction).

Differences:
1. Radioactivity: Most lanthanoids are non-radioactive (except Promethium). All actinoids are radioactive.
2. Oxidation States: Lanthanoids show limited oxidation states (+2, +3, +4). Actinoids show a wide range of oxidation states (up to +7) because the energy difference between 5f, 6d, and 7s orbitals is small.
3. Complex Formation: Actinoids have a much greater tendency to form complexes than lanthanoids.
Step 3: Final Answer:
Similarities include the common +3 oxidation state and filling of f-orbitals. Differences include radioactivity and the range of oxidation states.

Step 1: Understanding the Concept:
The lanthanide series consists of 14 elements from Cerium ( ) to Lutetium ( ). Most lanthanides are non-radioactive and occur naturally.
Step 2: Detailed Explanation:
Promethium ( , atomic number 61) is the only lanthanide element that does not have any stable isotopes. It is produced synthetically and is radioactive.
Step 3: Final Answer:
The radioactive element in the lanthanide series is Promethium.

Step 1: Understanding the Concept:
The color of transition metal ions is generally due to transitions of electrons. This requires the presence of partially filled -orbitals.
Step 2: Detailed Explanation:
1. For :
Atomic number of is 21. Configuration: .
For , all three valence electrons are removed. Configuration: .
Since the subshell is empty, there are no electrons to undergo transitions. Thus, it is colourless.

2. For :
Atomic number of is 25. Configuration: .
For , three electrons are removed. Configuration: .
It contains unpaired electrons in the subshell. These electrons can absorb specific frequencies of visible light to jump between split -orbital energy levels ( transition). The reflected/transmitted light gives the salt its color.
Step 3: Final Answer:
is colourless due to empty -orbitals ( ), while is coloured due to partially filled -orbitals ( ).

Step 1: Understanding the Concept:
According to the Aufbau principle, the expected configuration would be . However, certain elements show anomalies to gain extra stability.
Step 2: Detailed Explanation:
Chromium ( ) exhibits an exceptional configuration. One electron from the orbital shifts to the orbital.
This results in a configuration of .
This is because:
1. Symmetry: Half-filled subshells ( ) are more symmetrical and therefore more stable.
2. Exchange Energy: A half-filled subshell allows for maximum exchange of electron positions, leading to higher exchange energy and lower overall energy of the atom.
Step 3: Final Answer:
The observed electronic configuration of is .

Step 1: Understanding the Concept:
The magnetic moment of transition metal ions is calculated based on the number of unpaired electrons in their -orbitals.
Step 2: Key Formula or Approach:
Spin-only formula: Bohr Magnetons (BM), where is the number of unpaired electrons.
Step 3: Detailed Explanation:
Atomic number of Titanium ( ) is 22.
Electronic configuration of : .
In ion, three electrons are removed (two from and one from ).
Configuration of : .
Number of unpaired electrons, .


Step 4: Final Answer:
The magnetic moment of is 1.73 BM.

Step 1: Understanding the Concept:
First ionization enthalpy ( ) is the energy required to remove the first electron from an isolated gaseous atom.
In a transition series, generally increases from left to right due to increasing nuclear charge and decreasing atomic size.
Step 2: Detailed Explanation:
Zinc ( ) is the last element of the 3d series.
Electronic configuration of : .
In Zinc, both the 3d and 4s subshells are completely filled, which provides extra stability.
Additionally, because Zinc is at the end of the series, it has a high effective nuclear charge acting on its valence electrons.
Removing an electron from the stable, fully-filled orbital of Zinc requires significantly more energy compared to elements like , or .
Step 3: Final Answer: Zinc ( ) has the highest first ionization enthalpy among the given options.

Concept:
Magnetic moment of transition metal ions depends on the number of unpaired electrons and is calculated using the spin-only formula: where = number of unpaired electrons.
Step 1: Identify the Element
Atomic number 25 → Manganese (Mn)
Step 2: Divalent Ion Formation
All five d-electrons remain unpaired.
Step 3: Calculate Magnetic Moment

Conclusion:
The given statement is correct.

Concept:
Transition elements are defined as elements that have partially filled d-orbitals in their atoms or in at least one of their common oxidation states.
Explanation:

Zinc (Zn), Cadmium (Cd), and Mercury (Hg) belong to Group 12 of the periodic table.
Their electronic configurations have completely filled d-subshells. Even in their common ions (e.g., ), the d-orbitals remain fully filled.
Conclusion:
Since they do not have partially filled d-orbitals, Zn, Cd, and Hg are not considered true transition elements.