Electron Configuration and Orbital Notation: A Simple How-To
First of all, before we tackle on how to write the electron configuration and orbital notation of elements, we must know a few terms.
Orbitals are regions inside an energy level where the probability of finding an electron is very high. There are 4 different types of orbitals namely the s, p, d and f orbitals. They are different in the amount of electrons they can contain. The s orbital contains a maximum 2 electrons, the p orbital contains a maximum 6 electrons, the d orbital contains a maximum 10 electrons and the f orbital contains a maximum 14 electrons. An easy way to calculate the number of orbitals found in an energy level (n) is to use the formula n2. Therefore we know that the number of electrons in energy level 2 (n=2) will be 4.
The three principles involved in writing down electron configurations and orbital notations correctly are the Aufbau Principle, the Pauli Exclusion Principle and Hund’s Principle.
The Aufbau Principle states that electrons arrange to have the minimum amount of energy. This means that electrons start at the lowest orbital then increase the number of electrons step-by-step.
The Pauli Exclusion Principle states that there can only be two electrons in each orbital. This means that only two or less electrons can occupy the same orbital but must rotate in opposite directions.
Hund’s Principle states that the most stable arrangement of electrons is that which allows the maximum number of unpaired electrons. This arrangement minimizes electron-electron repulsions.
For our element Strontium, by applying the three principles and information on orbitals, we can write the electron configuration and orbital notation of Strontium as 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
Another way of expressing this and other electron configurations is to use the symbol for the noble gas preceding the element in question, which assumes its electron configuration, and add on the additional orbitals. So strontium, our example above, can be written as [Kr] 5s2.
*Here’s a tip to know what orbital the element you are finding for lies:
*A simple video to help you understand more
Kenrik Ng H3A, Chase Yao, H3F