Selenium electron configuration

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Selenium electron configuration
Selenium electron configuration

The electron configuration of selenium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4 or [Ar] 4s2 3d10 4p4.

Methods

We can write the electron configuration of selenium using four different methods:

#1 Using aufbau principle
#2 Using periodic table
#3 From its Bohr model
#4 From its orbital diagram

Let’s break down each method in detail.

Using aufbau principle

  • First, find electrons of selenium atom
Periodic table

The atomic number of selenium represents the total number of electrons of selenium. Since the atomic number of selenium is 34, the total electrons of selenium are 34.

  • Second, make a table of subshell and its maximum electrons

Calculate the maximum number of electrons each subshell can hold using the formula: 4ℓ + 2

Where, ℓ = azimuthal quantum number of the subshell

For s subshell, ℓ = 0
For p subshell, ℓ = 1
For d subshell, ℓ = 2
For f subshell, ℓ = 3

subshell max. electrons
s 2
p 6
d 10
f 14

This means that,

Each s subshell can hold maximum 2 electrons
Each p subshell can hold maximum 6 electrons
Each d subshell can hold maximum 10 electrons
Each f subshell can hold maximum 14 electrons

  • Finally, use aufbau chart and start writing electron configuration

Remember that we have a total of 34 electrons.

According to the aufbau principle, 1s subshell is filled first and then 2s, 2p, 3s… and so on.

Use 2 electrons for 1s subshell

By looking at the chart, you can see that electrons are first filled in 1s subshell. Each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 1s subshell.

So the electron configuration will be 1s2. Where, 1s2 indicates that the 1s subshell has 2 electrons.

Now we have used 2 electrons in the 1s subshell, so we have a total of 34 – 2 = 32 electrons left.

Use 2 electrons for 2s subshell

Looking at the chart, after 1s subshell now comes 2s subshell. Again, each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 2s subshell.

So the electron configuration will be 1s2 2s2. Where, 2s2 indicates that the 2s subshell has 2 electrons.

Again, we have used 2 electrons in the 2s subshell, so we have a total of 32 – 2 = 30 electrons left.

Use 6 electrons for 2p subshell

After 2s subshell now comes 2p subshell. Each p-subshell can hold a maximum of 6 electrons, so we will use 6 electrons for the 2p subshell.

So the electron configuration will be 1s2 2s2 2p6. Where, 2p6 indicates that the 2p subshell has 6 electrons.

Here, we have used 6 electrons in the 2p subshell, so we have a total of 30 – 6 = 24 electrons left.

Use 2 electrons for 3s subshell

After 2p subshell now comes 3s subshell. Each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 3s subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2. Where, 3s2 indicates that the 3s subshell has 2 electrons.

Here, we have used 2 electrons in the 3s subshell, so we have a total of 24 – 2 = 22 electrons left.

Use 6 electrons for 3p subshell

After 3s subshell now comes 3p subshell. Each p-subshell can hold a maximum of 6 electrons, so we will use 6 electrons for the 3p subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6. Where, 3p6 indicates that the 3p subshell has 6 electrons.

Here, we have used 6 electrons in the 3p subshell, so we have a total of 22 – 6 = 16 electrons left.

Use 2 electrons for 4s subshell

After 3p subshell now comes 4s subshell. Each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 4s subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2. Where, 4s2 indicates that the 4s subshell has 2 electrons.

Here, we have used 2 electrons in the 4s subshell, so we have a total of 16 – 2 = 14 electrons left.

Use 10 electrons for 3d subshell

After 4s subshell now comes 3d subshell. Each d-subshell can hold a maximum of 10 electrons, so we will use 10 electrons for the 3d subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10. Where, 3d10 indicates that the 3d subshell has 10 electrons.

Here, we have used 10 electrons in the 3d subshell, so we have a total of 14 – 10 = 4 electrons left.

Use last 4 electrons for 4p subshell

After 3d subshell now comes 4p subshell. Each p-subshell can hold a maximum of 6 electrons, but here we have only 4 electrons left, so we will use that 4 electrons for the 4p subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2 3d104p4. Where, 4p4 indicates that the 4p subshell has 4 electrons.

Therefore, the final electron configuration of selenium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4. And the condensed/abbreviated electron configuration of selenium is [Ar] 4s2 3d10 4p4.

Where, Ar is argon

Using periodic table

  • First, get periodic table chart with spdf notation
Periodic table blocks

The above image shows periodic table blocks.

The ‘s’ in s block represents that all s block elements have their valence electrons in s subshell. Similarly, the ‘p’ in p block represents that all p block elements have their valence electrons in p subshell. And so on for d block and f block.

  • Second, mark location of selenium on periodic table

Selenium is the p block element located in group 16 and period 4. Hence, mark the location of selenium on the periodic table as follows:

Mark location of selenium on periodic table
  • Finally, start writing electron configuration

Remember that: each s subshell can hold maximum 2 electrons, each p subshell can hold maximum 6 electrons, each d subshell can hold maximum 10 electrons, and each f subshell can hold maximum 14 electrons.

Start writing electron configuration from the very first element (i.e., hydrogen) all the way up to selenium.

Start from 1s and write till Se for full electron configuration

So the electron configuration of selenium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4.

From Bohr model

Selenium Bohr model

In the above image, 1 represents the 1st electron shell. Similarly, 2 represents the 2nd electron shell, 3 represents the 3rd electron shell, and 4 represents the 4th electron shell.

The 1st electron shell contains 1s subshell, the 2nd electron shell contains 2s and 2p subshells, the 3rd electron shell contains 3s, 3p, and 3d subshells, and the 4th electron shell contains 4s subshell.

We know that each s subshell can hold maximum 2 electrons, each p subshell can hold maximum 6 electrons, each d subshell can hold maximum 10 electrons, and each f subshell can hold maximum 14 electrons.

Also, we have to make sure that the electron configuration will match the order of aufbau principle (i.e., the 1s subshell is filled first and then 2s, 2p, 3s… and so on).

So the electron configuration of selenium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4.

Where,

1s2 indicates that the 1s subshell has 2 electrons
2s2 indicates that the 2s subshell has 2 electrons
2p6 indicates that the 2p subshell has 6 electrons
3s2 indicates that the 3s subshell has 2 electrons
3p6 indicates that the 3p subshell has 6 electrons
4s2 indicates that the 4s subshell has 2 electrons
3d10 indicates that the 3d subshell has 10 electrons
4p4 indicates that the 4p subshell has 4 electrons

From orbital diagram

Selenium orbital diagram

The above orbital diagram shows that the 1s subshell has 2 electrons, the 2s subshell has 2 electrons, the 2p subshell has 6 electrons, the 3s subshell has 2 electrons, the 3p subshell has 6 electrons, the 4s subshell has 2 electrons, the 3d subshell has 10 electrons, and the 4p subshell has 4 electrons.

So the electron configuration of selenium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4.

Next: Bromine electron configuration

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Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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