Lanthanoid contraction is caused due to :

1. the appreciable shielding on outer electrons by 4f electrons from the nuclear charge

2. the appreciable shielding on outer electrons by 5d electrons from the nuclear charge

3. the same effective nuclear charge from Ce to Lu

4. the imperfect shielding on outer electrons by 4f electrons from the nuclear charge

In the transition elements, the incoming electron occupies (n-1)d sublevel in preference to:

1. np

2. ns

3. (n-1)d

4. (n+1)s

The electronegativity of elements from group 1 to group 17 :

1. Decreases

2. Increases

3. Remains constant

4. All of the above

The electronic configuration of the most electropositive element is :

1. [He]2s¹

2. [Xe]6s¹

3. [He]2s²

4. [Xe]6s²

Which one of the following is an amphoteric oxide?

1. SO₂

2. B₂O₃

3. ZnO

4. Na₂O

Transition elements exhibit variable oxidation states because they release electrons from the following orbits:

1. ns and np orbits

2. (n-1)d and ns orbits

3. (n-1)d orbits

4. ns orbits

Elements of group IB  is called as:

Element that has the greatest tendency to lose an electron is :

The outer electronic configuration of Gd (Atomic no. 64) is:

1. 4f³ 5d⁵6d²

2. 4f⁸ 5d¹⁰6d²

3. 4f⁴ 5d⁴6d²

4. 4f⁷ 5d¹6s²

The radius of La³⁺ (at. no. 57) is 1.06 $\stackrel{°}{\mathrm{A}}$ The radius of Lu³⁺ (at.no. 71) might be:

1. 1.06  $\stackrel{°}{\mathrm{A}}$

2. 0.85  $\stackrel{°}{\mathrm{A}}$

3. 1.60  $\stackrel{°}{\mathrm{A}}$

4. 1.40  $\stackrel{°}{\mathrm{A}}$