The reason for lanthanoid contraction is:

1. Negligible screening effect of 'f' orbitals

2. Increasing nuclear charge

3. Decreasing nuclear charge

4. Decreasing screening effect

A diamagnetic lanthanoid ion among the following is :

(At. numbers:  Ce = 58, Sm = 62, Eu = 63, Yb = 70)

1. Ce²⁺

2. Eu²⁺

3. Sm²⁺

4. Yb²⁺

Among the following, the incorrect statement regarding interstitial compounds is:

1. They retain metallic conductivity.

2. They are chemically reactive.

3. They are much harder than the pure metal.

4. They have higher melting points than the pure metal.

Identify the mixture of metals that contain a non-metal as a constituent in it.

1. lnvar

2. Steel

3. Bell metal

4. Bronze

Which of the statements is not true?

1. On passing H₂S through acidified K₂Cr₂O₇ solution, a milky colour is observed

2. Na₂Cr₂O₇ is preferred over K₂Cr₂O₇ in volumteric analysis

3. K₂Cr₂O₇ solution in acidic medium is orange

4. K₂Cr₂O₇ solution becomes yellow on increasing the pH beyond 7

A pair among the following that have the same size is:

1. Fe²⁺, Ni²⁺

2. Zr⁴⁺, Ti⁴⁺

3. Zr⁴⁺ , Hf⁴⁺

4. Zn²⁺, Hf⁴⁺

Which of the following species is colourless?

1. ${\mathrm{TiF}}_6^{2-}$ and ${\mathrm{CoF}}_6^{3-}$ 

2. Cu₂Cl₂  and ${\mathrm{NiCl}}_4^{2-}$

3. ${\mathrm{TiF}}_6^{2-}$ and Cu₂Cl₂ 

4. ${\mathrm{CoF}}_6^{3-}$ and ${\mathrm{NiCl}}_4^{2-}$ 

identify the incorrect statement among the following:

(1) There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu.

(2) Lanthanoid contraction is the accumulation of successive shrinkages

(3) As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements

(4) Shielding power of 4f electrons is quite weak

More number of oxidation states are exhibited by the actinoids than by the lanthanoids. The main reason for this is:

(1) More energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals

(2) Lesser energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals

(3) Greater metallic character of the lanthanoids than that of the corresponding actinoids

(4) More active nature of the actinoids

In which of the following pairs are both the ions coloured in aqueous solution?

(1) Ni²⁺, Ti³⁺             

(2) Sc³⁺, Ti³⁺

(3) Sc³⁺, Co²⁺           

(4) Ni²⁺, Cu⁺

(At. no : Sc =21, Ti = 22, Ni = 28, Cu = 29, Co = 27)