The incorrect statement among the following is:

1.	Lanthanoids are good conductors of heat and electricity.
2.	Actinoids are highly reactive metals, especially when finely divided.
3.	Actinoid contraction is greater for element to element than Lanthanoid contraction.
4.	Most of the trivalent Lanthanoid ions are colorless in the solid-state.

Zr (Z = 40) and Hf (Z = 72) have similar atomic and ionic radii because of: 

1. Lanthanoid contraction

2. Having similar chemical properties

3. Belonging to the same group

4. Diagonal relationship

The correct order of ionic radii of Y³⁺, La³⁺, Eu³⁺, and Lu³⁺ is:

(Atomic nos. Y = 39, La = 57, Eu = 63, Lu = 71)

1. Y³⁺ < La³⁺ < Eu³⁺ < Lu³⁺

2. Y³⁺ < Lu³⁺ < Eu³⁺ < La³⁺

3. Lu³⁺ < Eu³⁺ < La³⁺ < Y³⁺

4. La³⁺ < Eu³⁺ < Lu³⁺ < Y³⁺

The basic character of the transition metal monoxides follows the order:
(Atomic nos. Ti = 22, V = 23, Cr = 24, Fe = 26)

The catalytic activity of transition metals is due to:

An incorrect statement among the following is :

Zn gives H₂ gas with H₂SO₄ and HCl but not with HNO₃ because:
 

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

1. Cr

2. Fe

3. Mn

4. V

The general electronic configuration of lanthanoids is:

1. (n – 2) f ^1–14 (n – 1) s² p⁶ d^0–1 ns²

2. (n – 2) f ^10–14 (n – 1) d^0–1 ns²

3. (n – 2) f ^0–14 (n – 1) d¹⁰ ns²

4. (n – 2) d^0–1 (n – 1) f ^1–14 ns²

A set of ions among the following that have a 3d² electronic configuration is:

1. ${\mathrm{Ti}}^{+},{\mathrm{V}}^{4+},{\mathrm{Cr}}^{6+},{\mathrm{Mn}}^{7+}$

2. ${\mathrm{Ti}}^{4+},{\mathrm{V}}^{3+},{\mathrm{Cr}}^{2+},{\mathrm{Mn}}^{3+}$

3. ${\mathrm{Ti}}^{2+},{\mathrm{V}}^{3+},{\mathrm{Cr}}^{4+},{\mathrm{Mn}}^{5+}$

4. ${\mathrm{Ti}}^{3+},{\mathrm{V}}^{2+},{\mathrm{Cr}}^{3+},{\mathrm{Mn}}^{4+}$