Colourless ion among the following is:

1.	Cr+4	2.	Sc+3
3.	Ti+3	4.	V+3

The oxo metal anions of the 3d series in which the metal exhibits an oxidation state equal to its group number is /are:

The electronic configuration of the last element of actinoids is :

1. Thorium, Th: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

2. Lawrencium, Lr: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

3. Neptunium, Np: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

4. Protactinium, Pa: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

The correct statement regarding the element silver(Ag) is: 

The enthalpy of atomization of transition metals is high due to :

1. High effective nuclear charge

2. A large number of valence electrons

3. Very strong metallic bonds

4. All of the above

The transition metals generally form coloured compounds due to :

Transition metals and their many compounds act as good catalysts due to :

Match the List I with List II:

The correct statement(s) about transition elements are: