Pt

Fe

W

Cu

Cast iron

Wrought iron

Stainless steel

Mild steel

C

Ni

Sand

Spiegeleisen

All three are coloured

All three are colourless

Only ${\rm{Z}}{{\rm{n}}^{2 + }}$ is colourless and ${\rm{N}}{{\rm{i}}^{2 + }}$ and ${\rm{C}}{{\rm{r}}^{3 + }}$ are coloured

Only ${\rm{N}}{{\rm{i}}^{2 + }}$ is coloured and ${\rm{Z}}{{\rm{n}}^{2 + }}$ and ${\rm{C}}{{\rm{r}}^{3 + }}$ are colourless

$La{\left( {OH} \right)_3}$

$Eu{\left( {OH} \right)_3}$

$Er{\left( {OH} \right)_3}$

$Lu{\left( {OH} \right)_3}$

Outermost and penultimate shells are incomplete

Both penultimate and prepenultimate shells are incomplete

Outermost shell is incomplete

Innermost shell is incomplete

Gives hardness to steel and can remove oxygen and sulphur

Helps the formation of oxides of iron

Can show highest oxidation state of +7

None of the above

${\rm{M}}{{\rm{n}}^{2 + }}$

${\rm{S}}{{\rm{c}}^{4 + }}$

${\rm{F}}{{\rm{e}}^{2 + }}$

${\rm{M}}{{\rm{n}}^{3 + }}$

${\left[ {CC{l_6}} \right]^2}$

${\left[ {GeC{l_6}} \right]^2}^ -$

${\left[ {SiC{l_6}} \right]^2}^ -$

${\left[ {SnC{l_6}} \right]^2}^ -$

Variable oxidation states

Formation of coloured compounds

Formation of interstitial compounds

Natural radioactivity

13 electrons have spin in one direction and 16 electrons in other direction

14 electrons have spin in one direction and 15 electrons in other direction

All the electrons have spin in one direction

None of the above