What are Patterns of Electrons? | General Chemistry 1

Can You See a Pattern of Electrons?

Yes, in fact, it's easier than most people think. Once you know the basics and with some practice, you'll come to see there are always patterns! And, finding those patterns will be much easier. To understand exactly what you are looking for, there are a few things to always keep in mind: 


Electrons always go to the lowest energy level possible

Why do electrons want to be in the lowest energy levels possible? Well, it's all thanks to quantum mechanics and classical physics governing this process.  Electrons are in their lowest energy level when they are closest to the nucleus. Electrons want to be in this position because it is the most stable state with an electron cloud of 0, meaning no charge.


Main Shells vs. Subshells

A shell is a type of composite structure that has many layers and each layer performs an important function. There are "main shells" and "subshells". The main ones, designated by numbers (eg 1st, 2nd, etc.) can be seen as the first in line while subshells - letters like s-, p-, d-, and f- relate to different categories. 


Know the Stable Energy Levels

It's pretty straightforward, with just a few breaks in a predictable pattern:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s

Take note that 4s comes before 3d, then the pattern continues with 4p, and so on. The reason is that the 4s subshell has a lower energy level.  There are exceptions to these particular rules for main shells which you will come across if you continue reading about electron configurations more in-depth.


The Letter Determines the Number of Subshell Electrons

While we're at it, what do the letters in s, p, d, f stand for? 


Look at the Atomic Number

The atomic number tells us the number of protons and electrons the atom contains. This is true for atoms that are in their atomic state, but ionic atoms are a whole different story. So, if you look at the periodic table and see that oxygen has an atomic number of 8, you know it has 8 electrons.


What are the Principles of Electron Configuration?

The Pauli exclusion principle, the Afbau Principle, and Hund's rule are three important rules to follow when assigning electrons to their orbits in an atom. The wavefunction solves for the Schrödinger equation which allows us to understand how many different properties we can observe from just one electron orbiting its respective shell without interfering with other shells around it.