How many outer-shell d electrons are there in each of the following transition-metal ions?

a) Mn(IV):

b) Co(III):

c) Fe(II):

d) Ni(II):

a)

Given

the oxidation number of Mn is +4

consider the ground state electronic configuration of Mn

1s2 2s2 2p6 3s2 3p6 3d5 4s2

in the

+4 state , four valence electrons are removed

so

the configuration now becomes

1s2 2s2 2p6 3s2 3p6 3d3

So

there are 3 electrons in outer shell d orbital

b)

given

the oxidation state of Co is +3

consider the ground state electronic configuration of Co

1s2 2s2 2p6 3s2 3p6 3d7 4s2

in the

+3 state , three valence electrons are removed

so

the configuration now becomes

1s2 2s2 2p6 3s2 3p6 3d6

So

there are 6 electrons in outer shell d orbital

c)

given

the oxidation state of Fe is +2

consider the ground state electronic configuration of Fe

1s2 2s2 2p6 3s2 3p6 3d6 4s2

in the

+2 state , three valence electrons are removed

so

the configuration now becomes

1s2 2s2 2p6 3s2 3p6 3d6

So

there are 6 electrons in outer shell d orbital

d)

given

the oxidation state of Ni is +2

consider the ground state electronic configuration of Ni

1s2 2s2 2p6 3s2 3p6 3d8 4s2

in the

+2 state , three valence electrons are removed

so

the configuration now becomes

1s2 2s2 2p6 3s2 3p6 3d8

So

there are 8 electrons in outer shell d orbital