Select the correct order of sizes for the following d-block elements.

Options

A. `Zr=Hf,Nb=Ta,Fe~=Co~=Ni`
B. `Zr^(4+) lt Zr, Nb^(3+) lt Ta^(3+), Fe^(3+) lt Fe^(2+) lt Fe`
C. `Zr^(4+)=Hf^(4+),Nb^(3+)=Ta^(3+),Fe lt Co lt Ni`
D. `Zr^(4+) lt Hf^(4+),Nb^(3+)=Ta^(3+),Ni lt Cu lt Co`

Answer

C

Explanation

`Zr=Hf,Nb=Ta ` due to lanthanide contraction.
and `Fe=[Ar]3d^(6)4s^(2)`
`Co=[Ar]3d^(7)4s^(2)`
`Ni=[Ar]3d^(8)4s^(2)`