Arsenic Valence Electrons (And How to Find them?)

So you have seen the above image by now, right?

Awesome! You can see that arsenic has 5 valence electrons.

But how can you say that Arsenic has 5 valence electrons
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How can you find these valence electrons?

Let’s discuss this in short.

Arsenic has 5 valence electrons because there are 5 electrons present in the outermost shell of the Arsenic (As) atom.

Now let’s see how you can easily find the valence electrons of Arsenic atom (As).

If you don’t want to read the texts, then you can also watch this video.

How to find the Valence Electrons? (2 Methods)

In order to find the valence electrons of Arsenic atom (As), you can use two methods.

Method 1: From the Periodic Table

To find out the valence electrons of Arsenic, you have to see the position of arsenic in the periodic table.

More specifically, you have to see the group wise position of Arsenic element in the periodic table.

From the above image, you can see that the Arsenic (As) is present in the group 15 of periodic table.
(Note: Group 15 is also called group 5A).

So, as the arsenic element is present in group 15, it has 5 valence electrons.

In this way, by knowing the position of arsenic element in periodic table, you can easily find its valence electrons.

Now let’s see another method for finding the number of valence electrons in arsenic.

Method 2: From the Electron Configuration

If you want to find the valence electrons of arsenic from its electron configuration, then you should know its electron configuration first.

Now there are many methods to write the electron configurations, but here I will show you the easiest method, i.e by using Aufbau principle.

Aufbau principle: The Aufbau principle simply states that the orbitals with the lower energy are filled first and then the orbitals with higher energy levels are filled.

According to the Aufbau principle, the orbitals are filled in the following order:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, and so on.

Also the maximum number of electrons that can be accommodated in s, p, d & f orbitals are mentioned in the below table.

Orbitals	Maximum capacity of electrons [1]
s	2
p	6
d	10
f	14

Now let’s try to find the electron configuration of Arsenic by using the Aufbau principle.

Electron Configuration of Arsenic:

Follow the steps mentioned below to get the electron configuration of Arsenic.

• To write the electron configuration of arsenic, we should first know the total number of electrons present in an arsenic atom.
• The arsenic atom has a total of 33 electrons because its atomic number is 33 and it is a neutral atom. ^[2]
• Now we have to fill these 33 electrons in the atomic orbitals according to the Aufbau principle.
• According to the Aufbau principle, the electrons will be filled first in 1s orbital, then in 2s orbital, then in 2p orbital, and so on…
• So from the Aufbau principle, we can get the electron configuration of the arsenic atom as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³. ^[3]

Now in this electron configuration of arsenic, we have to see the total number of electrons present in the highest energy level.

You can see in the electron configuration of arsenic (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³) that the highest energy level is 4. And the total number of electrons present in this energy level is 2 + 3 = 5.

So by knowing the electron configuration, we have found that the Arsenic has 5 valence electrons.

I hope you have understood the methods of finding the valence electrons in arsenic. 

See more related topics for your practice;
Selenium Valence Electrons
Bromine Valence Electrons
Krypton Valence Electrons
Indium Valence Electrons
Tin Valence Electrons