What is the ground-state electronic configuration of the chromium(III) ion, Cr^{3+}? (Atom… — JAMB UTME

What is the ground-state electronic configuration of the chromium(III) ion, $Cr^{3+}$ ? (Atomic number of $Cr = 24$ )

1s^2 2s^2 2p^6 3s^2 3p^6 3d^3

Neutral chromium (

Z = 24

) has the ground-state electron configuration

1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1

. When forming the

Cr^{3+}

ion, three electrons must be removed. Outer shell (

4s

) electrons are lost first, followed by

(n-1)d

electrons. Removing one electron from

4s

and two from

3d

gives the configuration

1s^2 2s^2 2p^6 3s^2 3p^6 3d^3

Determine the electronic configuration of neutral chromium (

Cr

)

Ground state

Cr

(

Z = 24

) is

1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1

Chromium exhibits an anomalous configuration due to the extra stability of a half-filled

3d

subshell.

Apply the rule for cation formation in transition metals

Electrons in the outermost shell (

n=4

4s

subshell) are lost before electrons in the inner subshell (

n=3

3d

subshell).

The

4s

electrons experience lower effective nuclear attraction in the ionized state and are situated at a higher principal energy level.

Remove 3 electrons to form

Cr^{3+}

Remove 1 electron from

4s

and 2 electrons from

3d

(3d^5 4s^1) - 3e^- = 3d^3 4s^0

Removing 1 electron from

4s

leaves

3d^5

; removing two more from

3d

leaves

3d^3

Electronic configuration of d-block transition metal cations

Estimated Time:1m 0s

Question