An element among the following that shows the maximum number of oxidation states is:

1. Cr

2. Fe

3. Mn

4. V

Which of the following factors is primarily responsible for the catalytic activity of transition metals?

Which of the following statements correctly describes lanthanoids?

The aqueous solution containing which one of the following ions will be colourless:

1. Fe²⁺

2. Mn²⁺

3. Ti³⁺

4. Sc³⁺

[Atomic number : Sc = 21, Fe = 26, Ti = 24, Mn = 25]

Which of the following is the most appropriate reason why transition elements exhibit high enthalpies of atomisation?

Which transition element does not exhibit variable oxidation states?

1. Manganese (\(Mn\))
2. Chromium(\(Cr\))
3. Scandium(\(Sc\))
4. Iron(\(Fe\))

The magnetic moment of a divalent ion (atomic number = 25) in aqueous solution is:

1. 4.34
2. 5.92
3. 6.12
4. 4.87
 

Which of the following reactions is an example of a disproportionation reaction?
1. 3\(MnO_{4}^{2-}\)+ 4 H⁺ → 2\(MnO_{4}^{-}\) + MnO₂ + 2H₂O
2. Na₂Cr₂O₇ + 2 KCl → K₂Cr₂O₇ + 2 NaCl
3. PCl₅ + H₂O → POCl₃ +  2HCl
4. 2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O

The well known element of lanthanoid series that exhibit +4 oxidation state, is:

1. Ac
2. Ce
3. Eu
4. Yb

The correct electronic configuration and spin only magnetic moment (BM) of Gd³⁺ (Z = 64), respectively, are:

1.  [Xe]5f⁷ and 8.9
2.  [Xe]4f⁷ and 7.9
3.  [Xe]5f⁷ and 7.9
4.  [Xe]4f⁷ and 8.9