The electronic configurations of Eu (Atomic no. 63), Gd (Atomic no. 64), and Tb (Atomic no. 65) are, respectively:

1.	[Xe] 4f6 5d1 6s2, [Xe]4f7 5d1 6s2, and [Xe] 4f9 6s2
2.	[Xe] 4f6 5d1 6s2, [Xe] 4f75d1 6s2, and [Xe]4f8 5d1 6s2
3.	[Xe] 4f7 6s2, [Xe]4f7 5d1 6s2, and [Xe] 4f9 6s2
4.	[Xe] 4f7 6s2, (Xe]4f8 6s2, and [Xe]4f8 5d1 6s2

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

1. $\left[Xe\right]4 f^8 6d^2$

2. $\left[Xe\right]4 f^9 5s^1$

3. $\left[Xe\right]4 f^7 5d^{1}6s^2$

4. $\left[Xe\right]4 f^6 5d^{2}6s^2$

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. HgCl, SnCl₂

3. FeCl₂, SnCl₂

4. FeCl₃, Kl

In acidic medium, H₂O₂ changes Cr₂O₇^–2 to CrO₅ which has two (–O – O–) bonds.
The oxidation state of Cr in CrO₅ is:

1. +5

2. +3

3. +6

4. -10

Which of the following statements is false?