The manganate and permanganate ions are tetrahedral, due to:

1.	The π-bonding involves the overlap of d-orbitals of oxygen with d-orbitals of manganese.
2.	The π-bonding involves the overlap of p-orbitals of oxygen with d-orbitals of manganese.
3.	Absence of π-bonding.
4.	The π-bonding involves the overlap of p-orbitals of oxygen with p-orbitals of manganese.

The reason for the lanthanoid contraction is:

1. negligible screening effect of 'f' orbitals.

2. increasing nuclear charge.

3. decreasing nuclear charge.

4. decreasing screening effect.

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

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

(Numbers in the parenthesis are atomic numbers).

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. $\left[Xe\right]4 f^6 5d^{2}6s^2$

Identify the incorrect statements related to lanthanons:
 

When neutral or faintly alkaline $KMn{O}_4$ is treated with potassium iodide, iodide ion is converted into 'X'. 'X' is:

1. $I_2$

2. $I{O}_4^{-}$

3. $I{O}_3^{-}$

4. $I{O}^{-}$