You are searching through the books, internet and asking a teacher and still don't understand what electron configuration is all about and how you can easily determine it? Then you are on the right place!
Today I’m going to show you the most easiest and trivial way to determine electron configuration and that is by using Periodic Table of Elements. For this purposes I’m using Periodic Table of Elements that exclusively made for electron configuration determination. You can download it directly from the picture or from the link below.
So let's dive into the matter!
Periodic Table of Elements for determination of Electron Configuration
Understand electron configuration notation
Electron configurations are written so as to clearly display the number of electrons in the atom as well as the number of electrons in each orbital. Each orbital is written in sequence, with the number of electrons in each orbital written in superscript to the right of the orbital name. The final electron configuration is a single string of orbital names and superscripts.
Notation of Electron Configuration
What is the electron configuration after all?
Simply said, the electron configuration is a distribution or arragement of electrons in an atom. Every element in Periodic Table of Elements has certain number of electrons that are differently "positioned" within an certain atom.
Your goal is to find out in which shells, subshells and orbitals those electrons can be found. Don't be intimidated by the terms shells, subshells and orbitals - I will show you that they can be easily found in an Periodic Table.
Then show me!
Ok, ok calm down. So let's take a closer look at this periodic table - as you can see, as any other periodic table, this one is also divided into rows (periods) and columns (groups). I have marked periods - there are seven of them as you can see, and they represent shells in electron configuration.
On the other hand, the subshells are represented with different colors - blue, orange, pink and green. Blue one is s subshell, green one is p subshell, orange is d and pink one at the bottom is f subshell. So - there are four subshells - s, p, d & f. They are also marked within yellow squares of each period (example below: Rb, rubidium can be found in fifth shell and s subshell)
The number of shell and subshell for Rubidium example
But what about orbitals?
The last step is to find orbitals. You will find the number of orbitals by counting the boxes which contain element in a single subshell (this sounds weird).
Let me show you what I mean.
For example if we want to find electron configuration of H, hydrogen it will be
shell: 1 (first period)
subshell: s (blue box)
orbital: 1 (as it is the first box in s subshell)
You can see notation of what I've written down below.
Electron configuration of Hydrogen, H
Another example is if we want to find electron configuration of He, helium it will be
shell: 1 (first period)
subshell: s (blue box)
orbital: 1 (as it is in the second box in s subshell)
Electron configuration of Helium, He
But this is not all there is, isn't it?
Okay, so we have determined three basic concepts of electron configuration: shells, subshells and orbitals - and, most importanly, how to find them on Periodic table of elements. Also, you have learned the basic notation of electron configuration (look at the examples of hydrogen and helium).
The next step is go to more advanced tasks, to see how the things are going.
Electron configuration of Magnesium, Mg
1. find Magnesium in the Periodic Table of Elements and determine it's atomic number (it is small number above "Mg"), which is 12
2. you see a sign with an arrow in PTE, "Start here and always go to the right"? Yep, that means if you want to determine electron configuration of Mg, you need to count all these boxes until you get to the Mg. But how?
Just follow the red arrows:
The first arrow gives:
The second arrow:
The third arrow:
And the last one:
3. the sum of these four arrows is Electron Configuration of Mg. Let's see:
4. let's recheck. The sum of number of orbitals (uppercase numbers) needs to be equal as the atomic number of Mg (12).
Well done! You have now successfully determined the electron configuration of magnesium, Mg.
Was it hard? Share with me your experience in comments. Do you have your own way of writing electron configuration?
Also, if you have difficulties in understanding Electron Configuration or just want to have a place where you will get it all and need more extended explanation take a look at my course Chemistry Exam: Electron configuration, Mass & Atomic Number where you can find absolutely everything about this topic.
"He who says he can, and he who says he can't are both usually right!"