Distribution of Electrons in Atomic Orbits
The planetary model of an atom was created by Neils Bohr. He was the first to indicate that the properties of the elements have a regular pattern. The electronic structure of an atom is based on the “Bohr atomic model.” He was the first to describe the arrangement of electrons in distinct orbits/shells (electronic configuration). He proposed that electrons are spread in electronic shells that are circular in shape (orbits). These electrons travel a defined distance around the nucleus in orbits.
Before understanding the concept of Electronic Configuration, let’s first understand some basic terms used with it as mentioned below:
Shells
It is based on the principal quantum number (n) which determines the maximum number of electrons that can be placed in a shell. The number of electrons in each shell is given by the formula 2n2 where n represents the shell number.
Subshells
It is based on an azimuthal quantum number which is widely denoted by ‘I’. At the same time, the azimuthal quantum number depends on the value of the principal quantum number (n). For example, if the value of shell n=3. The subshells corresponding to it will be s,p, and d with I=0, I=1, and I=2. These are the shells in which the actual distribution of electrons takes place. And the maximum number of electrons accommodated by a sub-shell is given by the formula 2(2I+1). The possible subshells and their resulting electronic configuration based on quantum number are given below.
| Value of principal quantum number | Azimuthal quantum number | Electronic configuration |
|---|---|---|
|
n=1 |
I=0 |
1s |
|
n=2 |
I=0 |
2s |
|
|
I=1 |
2p |
|
n=3 |
I=0 |
3s |
|
|
I=1 |
3p |
|
|
I=2 |
3d |
|
n=4 |
I=0 |
4s |
|
|
I=1 |
4p |
|
|
I=2 |
4d |
|
|
I=3 |
4f |
Electron Configuration
Electron Configuration of an element tells us how electrons are filled inside various orbitals of the atom. The distribution of electrons inside various orbital of atoms is very useful in explaining various properties of the atoms and their combination with other atoms. The electron configuration of the N (the most common element in the Earth’s atmosphere) is 1s2 2s2 2p4 as it has 7 electrons which are arranged in order as 2 is 1s orbital, 2 in 2s orbital, and 3 in 2p orbital.
Let’s have a look at how electrons are arranged around a nucleus for other atoms which rules are useful in achieving the right electron configuration and other in this article.
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