Advanced Electron Configuration


Electrons are essential components of an element and decide its reactivity and bonding. They have their own unique properties known as quantum numbers which makes them all unique, existing in a number of sub orbitals around a nucleus.

The electron configuration of elements plays an even deeper role in the structure of the periodic table. Extending understanding beyond shells it can be explored that there are subshells. To understand this we need to explore the concepts of electrons when considered as quantum particles. Electrons as previously explored are treated as particles, negative particles with a low mass that orbits the nucleus. But electrons can also be treated as waves. When treated as waves they can be assigned different properties.

Properties of electrons


There are 4 different orbital shapes, S, P, D and F. The S orbital is spherical, the P orbital is dumbell shaped, D orbitals are shaped like four-leaf clovers and F orbitals are a lot more complicated as seen in the image.

Distance from the nucleus

This simply signifies which shell it exists in such as 1 for the first shell closest to the nucleus etc.


Electrons come in pairs and they are either spin up or spin down, this is the direction they are moving in the electron cloud. When electrons fill up in an orbital as a pair they have opposite spins.

To write this electron configuration we need to combine these three elements. In the example of Helium. Helium has the electron configuration 1s2. This represents that the subshell is s-shaped (spherical) it is in the first shell 1s and the final part means it has 2 electrons in that shell hence the configuration 1s2.

If we look at an example we have seen before such as Lithium. Lithium, when considered under the basic electron configurations, has the annotation 2,1. But if we look at the periodic table we can separate it into areas where there are S P D and F blocks.

If we use the periodic table to look at Lithiums subshells it has configuration 1s2 2s1 the first shell 1s2 this means it is shell 1, it is s-shaped and it has 2 electrons in its shell. It also has a 2s1 shell. This means the second shell is also s-shaped and has 1 electron.

If we look at the example of Fluorine it is located in the P subshell area. It has the configuration 1s2 2s2 2p5. From this, it can be seen that Fluorine’s 1st shell has 2 electrons and is s-shaped (spherical), the second shell actually has 2 parts. The first part has 2 electrons in an s-shaped orbital hence the 2s2 but it also has 5 electrons that exist in the p orbital that is dumbbell shaped, hence the 2p5 part.

Terms in section
Electron configuration

The electron configuration is the numerical layout of electrons in the orbitals around the atom. Can be done simply for example lithium has 3 electrons and has 2 in the first shell (as this is the maximum) and 1 in the second shell giving it the configuration 2,1.


The shell is the path that electrons follow outside the nucleus. Shells can be considered as energy levels and the further away from the nucleus the higher in energy.


An orbit is the circular or dumbbell shaped motion that the electrons follow around the nucleus. Much like the planets orbiting the sun


The nucleus is the term given to the centre of the atom comprising of the proton and neutron

Quantum particle

A quantum particles is the smallest physical particle that can exist without being broken down. Electrons are quantum particles as they cannot be broken down further. Quantum particles like electrons have properties that make them unique such as their spin and energy level


A wave is a term in chemistry to describe when electrons can be treated as waves due to their properties and energy


Subshells are the broken down 3d structure of the electrons and the path they take around the nucleus. Each subshell can occupy a different space and arrangement as electrons are treated as waves. Each subshell has a different path for the electron, different energy level and different number of electrons it can hold

S shell

An S shell is a spherical shaped shell that can hold two electrons with opposite spin

P shell

A P shell is a dumbbell shaped shell in three axis creating 3 shells that can hold 6 electrons in 3 pairs

D shell

A d sell is a more complex subshell much like the P orbital but in 2 axis. Can also be between axis. Can hold 10 electrons in 5 pairs.

F shell

The F shell is much more complicated than d orbitals and have a possible 7 quantum numbers so can be very varied in shapes. They can hold 14 electrons in 7 pairs


Spin is a property of electrons when in energy levels they will either be spin up or spin down


The Actinides of the Expanded Periodic Table


Evolution of the Atom