Question

Predict the ground-state electron configuration of the following ions. Write your answers in abbreviated form, that is, beginning with a noble gas in brackets.a). Cr2+b.)Cu2+c.)Co3+

Answer 1

These are three questions and three complete answers

Answer:

a) Cr²⁺: [Ar] 4s² 3d²

b) Cu²⁺: [Ar] 4s² 3d⁷

c) Co³⁺: [Ar] 4s² 3d⁴

Explanation:

a) Cr²⁺

• Z = 24

• Number of protons: 24

• Number of elecrons of the neutral atom: 24

• Charge of the ions: + 2

• Number of electrons of the ion: 24 - charge = 24 - 2 = 22.

• Electron configuration:

       Fill the orbitals in increasing order of energy. Using Aufbau's rules the order is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ .....

       Hence, for 22 electrons you get:

       1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d²

• Abbreviated notation: since the last complete level is the number 3s² 3p⁶, you use the noble gas of the period 3, which is Ar, and the configuration is:

       

        [Ar] 4s² 3d²

b) Cu²⁺

• Z = 29

• Number of protons: 29

• Number of elecrons of the neutral atom: 29

• Charge of the ion: + 2

• Number of electrons of the ion: 29 - charge = 29 - 2 = 27.

• Electron configuration:

       Fill the orbitals in increasing order of energy. Using Aufbau's rules the order is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ .....

       Hence, for 27 electrons you get:

       1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷

• Abbreviated notation: since the last complete level is the number 3s² 3p⁶, you use the noble gas of the period 3, which is Ar, and the configuration is:

       

        [Ar] 4s² 3d⁷

c) Co³⁺

• Z = 27

• Number of protons: 27

• Number of elecrons of the neutral atom: 27

• Charge of the ion: + 3

• Number of electrons of the ion: 27 - charge = 27 - 3 = 24.

• Electron configuration:

       Fill the orbitals in increasing order of energy. Using Aufbau's rules the order is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ .....

       Hence, for 24 electrons you get:

       1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴

• Abbreviated notation: since the last complete level is the number 3s² 3p⁶, you use the noble gas of the period 3, which is Ar, and the configuration is:

       

        [Ar] 4s² 3d⁴