The metal ions that have the calculated spin only magnetic moment value of 4.9 B.M.$4.9\text{ B.M.}$ are: A. Cr²⁺$\mathrm{Cr}^{2+}$ B. Fe²⁺$\mathrm{Fe}^{2+}$ C. Fe³⁺$\mathrm{Fe}^{3+}$ D. Co²⁺$\mathrm{Co}^{2+}$ E. Mn³⁺$\mathrm{Mn}^{3+}$ Choose the correct answer from the options given below:

Related Formula

Core Logic

Analyzing each statement based on inorganic chemistry principles:

• Statement A is false: Because their d$d$-subshell is completely full (d¹⁰$d^{10}$), these elements do not form strong metallic bonds. As a result, they exhibit the lowest enthalpy of atomization in their respective periods.
• Statement B is true: Zn$\text{Zn}$ and Cd$\text{Cd}$ show only a stable +2$+2$ oxidation state, whereas Hg$\text{Hg}$ exhibits variable states forming both +1$+1$ (as Hg₂²⁺$\text{Hg}_2^{2+}$) and +2$+2$.
• Statement C is false: With a fully paired d¹⁰$d^{10}$ subshell, their compounds lack unpaired electrons and are explicitly diamagnetic.
• Statement D is true: Due to weak metallic bonds, these elements have low melting points and are classified as soft metals.

Step 1: Selection Verification

Statements B and D are true, matching choice (1).

Pattern Recognition

Group 12 metals have a full d¹⁰$d^{10}$ subshell, leading to exceptionally weak metallic bonding, low enthalpies of atomization, and diamagnetic characteristics.

Chapter Mix

Class 12 Chemistry: d and f Block Elements

Related Formula

Dissolution reaction pathway:

Core Logic

The reaction yields sodium tetrahydroxoplumbate(II), [Pb(OH)₄]²⁻$[\text{Pb(OH)}_4]^{2-}$. The charge of the complex species is -2$-2$ (dianionic), and it binds 4 hydroxo coordination ligands, matching a coordination number of four.

Chapter Mix

Class 12 Chemistry: d-and f-Block Elements Class 12 Chemistry: Coordination Compounds

Step 1: Production of Reddish Fumes

Reddish brown vapors (B) are chromyl chloride (CrO₂Cl₂$CrO_2Cl_2$).

Step 2: Conversion to Yellow Solution

Yellow solution (C) corresponds to sodium chromate (Na₂CrO₄$Na_2CrO_4$).

Pattern Recognition

Chloride detection signature: Cl^- arrow CrO₂Cl₂ (red-brown) arrow Na₂CrO₄ (yellow chromate).$\text{Cl}^- \rightarrow \text{CrO}_2\text{Cl}_2\text{ (red-brown)} \rightarrow \text{Na}_2\text{CrO}_4\text{ (yellow chromate)}.$

Chapter Mix

Class 12 Chemistry: d-and f-Block Elements

Core Logic

The noble gas configuration of Xenon (Z=54$Z=54$) provides the primary core layout. For Neodymium (Z=60$Z=60$), the 6 remaining valence electrons distribute into the inner 4f$4\text{f}$ orbital subshell rather than filling the 5d$5\text{d}$ subshell due to shielding effects. This results in an absolute atomic ground state electronic configuration of [Xe] 4f⁴ 6s²$\text{[Xe]} 4\text{f}^4 6\text{s}^2$.

Pattern Recognition

Lanthanide filling sequences generally bypass 5d$5d$ progression except for specific exceptions (La, Gd, Lu).

Chapter Mix

Class 12 Chemistry: d-and f-Block Elements

Core Logic

Potassium permanganate (KMnO₄$KMnO_4$) is a strong oxidizing agent. When heated to 513K$513\mathrm{K}$, it undergoes thermal decomposition to give potassium manganate (K₂MnO₄$K_2MnO_4$), manganese dioxide (MnO₂$MnO_2$), and oxygen gas (O₂$O_2$).

The balanced chemical equation is:

Step 1: Final Identification

The products formed along with O₂$O_2$ are K₂MnO₄$K_2MnO_4$ (green) and MnO₂$MnO_2$ (black).

Chapter Mix

Class 12 Chemistry: d and f Block Elements