There are 14 elements in actinoid series. Which of the following elements does not belong to this series?

1. U

2. Np

3. Tm

4. Fm

Identify the amphoteric oxides from the list provided:

${\mathrm{Mn}}_2{\mathrm{O}}_7, {\mathrm{CrO}}_3, {\mathrm{Cr}}_2{\mathrm{O}}_3, \mathrm{CrO}, {\mathrm{V}}_2{\mathrm{O}}_5, {\mathrm{V}}_2{\mathrm{O}}_4$

1. ${\mathrm{V}}_2{\mathrm{O}}_5, {\mathrm{Cr}}_2{\mathrm{O}}_3$

2. ${\mathrm{Mn}}_2{\mathrm{O}}_7, {\mathrm{CrO}}_3$

3. $\mathrm{CrO}, {\mathrm{V}}_2{\mathrm{O}}_5$

4. ${\mathrm{V}}_2{\mathrm{O}}_5, {\mathrm{V}}_2{\mathrm{O}}_4$

Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?

1. They have high melting points in comparison to pure metals.

2. They are very hard.

3. They retain metallic conductivity.

4. They are chemically very reactive.

Which of the following statements does not hold true?

The reason for not utilizing HCl to acidify the medium in oxidation reactions involving KMnO₄ (in an acidic environment) is:

Which has highest melting point?

The colour of KMnO₄ is due to

Which of the following element does not show a variable oxidation state?

With F highest stable oxidation state of Mn is-

${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-} + \mathrm{X} \stackrel{{\mathrm{H}}^{+}}{\to } {\mathrm{Cr}}^{3+} + {\mathrm{H}}_2\mathrm{O} +$ oxidised product of X
X in the above reaction can not be:
 

1. ${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$

2. ${\mathrm{Fe}}^{2+}$

3. ${\mathrm{SO}}_4^{2-}$

4. ${\mathrm{S}}^{2-}$