The reason for a greater range of oxidation states in actinoids is attributed to:

1. Actinoid contraction

2. 5f, 6d and 7s levels having comparable energies.

3. 4f and 5d levels being close in energies.

4. The radioactive nature of actinoids

Match  Column-I with Column-II and mark the most appropriate option:

When copper is heated with conc. HNO₃ it produces:

1. Cu(NO₃) and NO

2. Cu(NO₃)₂, NO and NO₂

3. Cu(NO₃)₂ and N₂O

4. Cu(NO₃)₂ and NO₂

Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?

1. $\left[Xe\right]4<mspace\; width="1em"></mspace>f^8<mspace\; width="1em"></mspace>6d^2$

2. $\left[Xe\right]4<mspace\; width="1em"></mspace>f^9<mspace\; width="1em"></mspace>5s^1$

3. $\left[Xe\right]4<mspace\; width="1em"></mspace>f^7<mspace\; width="1em"></mspace>5d^{1}6s^2$

4. $\left[Xe\right]4<mspace\; width="1em"></mspace>f^6<mspace\; width="1em"></mspace>5d^{2}6s^2$

A pair among the following have nearly the same atomic radii:

(Numbers in the parenthesis are atomic numbers).

Which of the following processes does not involve the oxidation of iron?

The number of d -electrons in Fe²⁺ (atomic number  Z = 26)  is different from the number of:
1. s-electrons in Mg (Z = 12)
2. p-electrons in Cl (Z = 17)
3. d-electrons in Fe (Z = 26)
4. p-electrons in Ne (Z = 10)

The pair of compounds that can exist together is:

1. FeCl₃, SnCl₂

2. HgCl₂, SnCl₂

3. FeCl₂, SnCl₂

4. FeCl₃, Kl