The correct statement(s) about interstitial compounds is/are:

1.	Transition elements are large in size and contain multiple interstitial sites.
2.	Transition elements can trap atoms of other elements.
3.	Interstitial compounds are chemically inert.
4.	All of the above.

The spin-only magnetic moment of ${\mathrm{Ce}}^{3+}$ is:
1. 3.25
2. 1.73
3. zero
4. 4.21

1. ${\mathrm{Ti}}^{3+},{\mathrm{V}}^{3+},$ ${\mathrm{Cu}}^{+}$

2. ${\mathrm{Sc}}^{3+},$ ${\mathrm{Mn}}^{2+},$ ${\mathrm{Fe}}^{3+}$

3. ${\mathrm{Ti}}^{3+},{\mathrm{V}}^{3+},$ ${\mathrm{Mn}}^{2+},$ ${\mathrm{Fe}}^{3+},$ $$ ${\mathrm{Co}}^{2+}$

4. None of the above.

The correct reactions among the following are:

$\mathrm{a}.$ ${\mathrm{MnO}}_4^{-}+{\mathrm{H}}^{+}+{\mathrm{Fe}}^{2+}\to 2{\mathrm{Mn}}^{2+}+{\mathrm{Fe}}^{3+}+{\mathrm{H}}_2\mathrm{O}$
$\mathrm{b}.$ ${\mathrm{C}}_2{\mathrm{O}}_4^{2-}+{\mathrm{MnO}}_4^{-}+{\mathrm{H}}^{+}\to {\mathrm{Mn}}^{2+}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2$
$\mathrm{c}.$ ${\mathrm{SO}}_2+{\mathrm{MnO}}_4^{-}+{\mathrm{H}}^{+}\to {\mathrm{Mn}}^{2+}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{SO}}_3$

Which of the following statements is/are correct?  

 1. a  only
 2. a and c only
 3. b only
 4. b and c only

The correct statement regarding inner transition elements is:

The most common oxidation state for lanthanoids and actinoids is:

The correct statement(s) about transition elements is/are:  

Which of the following correctly explains the positive $\mathrm{E}°({\mathrm{M}}^{2+}/\mathrm{M})$ value for copper (+0.34 V)?