Transition metals and their many compounds act as good catalysts due to :

1.	Variable oxidation states	2.	Unstable intermediate
3.	Provide a suitable surface	4.	All of the above

Transition metals show paramagnetic behaviour due to:
1. Paired electrons in the (n-1) d-orbitals
2. Unpaired electrons in the (n-1) d-orbitals
3. Due to \(d^{10},\) and \(d^{0}\) configuration
4. None of the above

Correct statements amongst the above are:

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

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: