Actinium Electron Configuration:7 Easy Steps on How to Write

Actinium is the inner transition metal in the periodic table having an atomic weight of 227u. Let us study the electronic configuration of Actinium in detail.

Ac is the first element of the actinide series, where it has filled 4f orbital and for this reason, it considers an f block element, although the valence electrons are present in 7s orbital. It is a soft, white radioactive metal present in the uranium series.

As per its electronic configuration, the stable oxidation state of Ac is +2 and +3. Now in this article, we should discuss the electronic configuration of Ac, along with the orbital diagram, electronic notation, ground, and excited state electronic configuration with proper explanation.

1. How to write the Actinium electron configuration

Ac is the 7th-period element so it has 89 electrons and those electrons should be arranged properly in the electronic configuration by the following steps,

Step 1- Arrangement of the orbital by energy order

We should arrange all the orbital by increasing the order of their energy as per Aufbau’s principle by using the n+l rule, where n is the principal quantum number and it should be noted as 1, 2, 3.. and l is the azimuthal quantum number it is noted as s,p,d,f. So, the orbitals for Ac like 1s<2s<2p<3s<3p<4s<3d<4p<5s…

Step 2- Filling the electron in each shell of orbital

Now we fill the electrons in each respective orbital by Hund’s rule, where first we fill electrons in each shell and if there are more electrons left then we go for pairing. Pairing the electron at first is not allowed. As example we filled p orbital by one electron in each shell and then go for pairing.

Step 3- pairing the electron following the perfect spin

When we paired the electron in each shell we should follow that both electrons should be in an opposite spin as per Pauling’s exclusion principle. Like s orbital can contains a maximum of two electrons and both should be in opposite spin and those electrons are written at the superscript of each shell.

2. Actinium electron configuration diagram

Ac has 89 electrons and all the electrons should be placed in the respective electronic shell as per the above three principles,

First, 1s will be filled by two electrons as it has lower energy and it has one orbital, and each orbital consists maximum of two electrons with opposite spin.
After 1s, 2s orbital will be filled by two electrons as per energy order
After 2s, the 2p orbital will be filled as per energy order and it has three orbitals so it can accumulate a maximum of six electrons.
After 2p, the 3s orbital is filled by two electrons as per higher energy than the previous one.
After 3s, the 3p orbital will be filled by six electrons as it has three orbitals and more energy.
After 3p, the 4s orbital will be filled by two electrons as it has higher energy for a higher principle quantum number.
After 4s, the 3d orbital will be filled due to effective nuclear charge and shielding effect it has higher energy than 4s and the d orbital has five subshells so it can accumulate a maximum of ten electrons.
After 3d, the 4p orbital will be filled by six electrons.
After 4p, the 5s orbital is filled by two electrons as per energy.
After 5s, the 4d orbital is filled by a maximum of ten electrons as it has more energy than 5s.
After 4d, the 5p orbital is filled by the six electrons.
After 5p, the 6s orbital is filled by two electrons.
After 6s, 4f orbital will be filled by a maximum of 14 electrons as f orbital contains seven subshells and due to poor screening effect, it has more energy than the former.
After 4f, the 5d orbital will be filled by 10 electrons.
After 5d, 6p orbital will be filled by the six electrons.
After 6p, the 7s orbital is filled by two electrons.
And lastly, the 6d orbital is filled by the remaining one electron.
So, all the 87 electrons will be filled in the diagram will be –

Screenshot 2022 11 18 203336 — Actinium Electron
Configuration diagram

3. Actinium electron configuration notation

The electronic configuration notation of Actinium is symbolized as –

[Rn]6d¹7s²,

This notation contains 89 electrons where Rn has 86 electrons so here we use noble gas configuration. The remaining extra 3 electrons are placed to the next 7s and 6d orbital by the energy order. It will place the availability of the orbital as per the principle quantum number.

4. Actinium unabbreviated electron configuration

The unabbreviated electronic configuration of Actinium is,

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f¹⁴5s²5p⁶5d¹⁰6s²6p⁶6d¹7s²

The Actinium unabbreviated electron configuration consists of a total of 89 electrons which are filled as follows –

Two electrons are present in 1s orbital.
Two electrons in 2s orbital.
Six electrons in 2p orbital.
Two electrons in 3s orbital.
six electrons in 3p orbital.
Ten electrons in 3d orbital.
Two electrons in 4s orbital.
Six electrons in 4p orbital.
Ten electrons in 4d orbital.
Fourteen electrons in 4f orbital.
Two electrons in 5s orbital.
Six electrons in 5p orbital.
Ten electrons in 5d orbital.
Two electrons in 6s orbital.
Six electrons in 6p orbital.
two electrons in 7s orbital.
One electron in 6d orbital.

5. Ground state Actinium electron configuration

Ac ground state electronic configuration is,

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f¹⁴5s²5p⁶5d¹⁰6s²6p⁶6d¹7s²Which is also its unabbreviated form where all the 87 electrons are suitably placed in proper orbital by respective energy order.

Screenshot 2022 11 18 203550 — Actinium Ground State
Electronic Configuration

6. Excited state of Actinium electron configuration

Ac excited state electronic configuration will be,

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f¹⁴5s²5p⁶5d¹⁰6s²6p⁶6d²7s¹. Here one electron from the 7s orbital shifted to the higher energy orbital 6d by providing energy. The promotional energy between 6d and 7s is low due to the relativistic effect of 6s and 7s as well. The electron will not be paired in 6d as per Hund’s rule.

Screenshot 2022 11 18 203720 — Actinium Excited State
Electronic Configuration

7. Ground state Actinium orbital diagram

The Actinium ground state orbital diagram is the presence of 89 electrons per shell around the nucleus as per quantum number and it needs 7 shells to arrange those 89 electrons and they are,

K -shell = containing two electrons (1s¹)
L-shell = containing 8 electrons (2s²2p⁶)
M-shell = containing 18 electrons (3s²3p⁶3d¹⁰)
N-shell = containing 32 electrons (4s²4p⁶4d¹⁰4f¹⁴)
O-shell = containing 18 electrons(5s²5p⁶5d¹⁰)
P-shell = containing 9 electrons(6s²6p⁶6d¹)
Q-shell = containing 2 electrons(7s²)
The orbital diagram of Actinium will be-

Screenshot 2022 11 18 203901 — Actinium Orbital Diagram

Conclusion

The 4f orbital of Ac is deep-seated for this reason the 6d and 7s orbital of Ac is always involved in the bond formation. So, it can exist stable +3 oxidation state and mainly form molecules with halogen as tri-coordinated. Some of the organometallic compounds of Ac are also known but the ligand is not directly involved with 4f orbital.

Also Read:

Biswarup Chandra Dey

Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.