Electronic distribution: what is it and examples

Electron distribution or electron configuration the way chemical elements are ordered considering the number of electrons they have and their proximity to the atomic nucleus.

Electronic tiered distribution

After several atomic models emerged, the Bohr model suggested organizing the electrosphere into orbits.

The electrons are organized and distributed through the electronic layers, some being closer to the nucleus and others farther away.

The farther away from the nucleus, the more energy the electrons have

Then came the 7 electronic layers (K, L, M, N, O, P and Q), which are represented by the horizontal lines numbered 1 to 7 in the periodic table.

Elements on the same lines have the same maximum number of electrons and also the same energy levels.

Thus, it is possible to observe that electrons are in energy levels and sub-levels. So each has a certain amount of energy.

Energy level	Electronic Layer	Maximum Number of Electrons
1°	K	2
2°	L	8
3°	M	18
4°	N	32
5°	O	32
6°	P	18
7°	Q	8

THE valence layer it is the last electronic layer, that is, the outermost layer of the atom. According to

Octet Rule, atoms have a tendency to stabilize and become neutral.

This happens when they have the same amount of protons and neutrons, with eight electrons in the last electron shell.

Later, the energy sublevels appeared, represented by the lowercase letters s, p, d, f. Each sublevel supports a maximum number of electrons:

sublevels	Maximum number of electrons
s	2
P	6
d	10
f	14

Pauling diagram

The American chemist Linus Carl Pauling (1901-1994) studied atomic structures and developed a scheme that is still used today.

Pauling found a way to put all the energy sublevels in ascending order, using the diagonal direction. The scheme became known as the Pauling diagram.

Linus Pauling diagram

Ascending order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁶

Note that the number indicated in front of the energy sublevel corresponds to the energy level.

For example, in 1s²:

• s indicates the energy sub-level
• 1 indicates the first level, located on layer K
• exponent 2 indicates the number of electrons in this sublevel

How to do electronic distribution?

To better understand the electronic distribution process, look at the solved exercise below.

1. Make the electronic distribution of the element Iron (Fe) which has atomic number 26 (Z = 26):

When applying the Linus Pauling Diagram, the diagonals are traversed in the direction indicated in the model. The energy sub-levels are filled with the maximum number of electrons per electron shell, until completing the element's 26 electrons.

To make the distribution, pay attention to the total number of electrons in each sublevel and in the respective electronic layers:

K - s²
L - 2s² 2p⁶
M - 3s² 3p⁶ 3d¹⁰
N - 4s²

Note that it was not necessary to do the electronic distribution in all layers, since the atomic number of Iron is 26.

Thus, the electronic distribution of this element is represented as follows: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶. The sum of the exponent numbers totals 26, that is, the total number of electrons present in the Iron atom.

If the electronic distribution is indicated by layers, it is represented as follows: K = 2; L = 8; M = 14; N = 2.

Take the opportunity to test your knowledge in Exercises on Electronic Distribution.

At periodic table, this is shown as follows:

Electronic distribution of iron on the periodic table

Read too:

• Electronic Affinity
• Quantum Numbers
• Exercises on the Periodic Table
• Exercises on Organizing the Periodic Table