Question 33 of 44intermediate🔧 ApplyLong Answer5 marks

Write down the number of 3d electrons in each of the following ions: Ti2+Ti^{2+}, V2+V^{2+}, Cr3+Cr^{3+}, Mn2+Mn^{2+}, Fe2+Fe^{2+}, Fe3+Fe^{3+}, Co2+Co^{2+}, Ni2+Ni^{2+} and Cu2+Cu^{2+}. Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

Correct Answer

Number of 3d Electrons:

Ion3d ConfigurationNumber of 3d Electrons
Ti²⁺3d²2
V²⁺3d³3
Cr³⁺3d³3
Mn²⁺3d⁵5
Fe²⁺3d⁶6
Fe³⁺3d⁵5
Co²⁺3d⁷7
Ni²⁺3d⁸8
Cu²⁺3d⁹9

Occupancy of 3d Orbitals in Octahedral Hydrated Ions:

In octahedral complexes, the five d orbitals split into two sets: t₂g (lower energy, 3 orbitals) and eg (higher energy, 2 orbitals). For hydrated ions, water acts as a weak field ligand, resulting in high-spin configurations where electrons occupy orbitals singly before pairing.

IonConfigurationOrbital Occupancy
Ti²⁺3d²t₂g² eg⁰
V²⁺3d³t₂g³ eg⁰
Cr³⁺3d³t₂g³ eg⁰
Mn²⁺3d⁵t₂g³ eg²
Fe²⁺3d⁶t₂g⁴ eg²
Fe³⁺3d⁵t₂g³ eg²
Co²⁺3d⁷t₂g⁵ eg²
Ni²⁺3d⁸t₂g⁶ eg²
Cu²⁺3d⁹t₂g⁶ eg³
Exercise: EXERCISES | Q: 4.36 | (Chapter: 29)
For More Understanding

Explanation

The answer uses Table 4.1 to determine ground state electronic configurations of transition metals, then removes electrons from 4s before 3d to form ions. Table 4.7 and Table 4.8 confirm the 3d configurations for these ions. For octahedral occupancy, water being a weak field ligand means high-spin arrangements where electrons fill t₂g orbitals first (following Hund's rule) before occupying eg orbitals.

Solution Steps

  1. Step 1: From Table 4.1, identify ground state configurations: Ti(3d²4s²), V(3d³4s²), Cr(3d⁵4s¹), Mn(3d⁵4s²), Fe(3d⁶4s²), Co(3d⁷4s²), Ni(3d⁸4s²), Cu(3d¹⁰4s¹)

  2. Step 2: Remove electrons from 4s first, then 3d to form ions

  3. Step 3: Verify configurations using Tables 4.7 and 4.8

  4. Step 4: For octahedral hydrated ions, apply high-spin configuration (weak field ligand H₂O): electrons occupy t₂g singly first, then eg orbitals

PreviousNext