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Electronic configuration

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Explainer Video

Tutor: Aimee LeBrun

Summary

Electronic configuration

In a nutshell

Electrons orbit the nucleus in shells. The electronic configuration is the arrangement of electrons in the shells around the nucleus. Each atom from an element will have a different number of electrons and therefore a different electronic configuration.

Electron shells

Definition

Electron shells are shells around the nucleus that occupy electrons.

Note: Electron shells are also known as energy levels.

Filling electron shells

Electrons occupy the lowest available energy levels (or shells). This means that the lowest energy levels will fill with electrons first. Then, it's important to know that each shell can only hold a maximum number of electrons. This is shown below.

sHELL NUMBER	MAXIMUM NUMBER OF ELECTRONS
First shell	Two
Second shell	Eight
Third shell	Eight
Fourth shell	Eight

Drawing electron shell diagrams

PROCEDURE

1.	Find the element of the atom needed to be drawn in the periodic table.
2.	Use the atomic number to work out how many electrons the atom will have.
3.	Draw the empty electron shells around the nucleus.
4.	Add the correct number of electrons to the shells, filling the inner shell with a maximum of two electrons first. Fill subsequent shells with a maximum of eight electrons.

Example

Draw the electron shell diagram for an atom of beryllium and write the electronic configuration of beryllium.

Beryllium has an atomic number of four, so will hold four electrons.

Draw the empty electron shells and then fill the shells with the four electrons.

The electronic configuration of beryllium is $\underline{2.2}$ .

Electron arrangement and the periodic table

ELECTRON structure fEATURE	RELATION TO THE PERIODIC TABLE
Number of outer shell electrons	The group number
Number of electron shells	The period number
Number of crosses (the number of electrons)	The atomic number
Total number of outer shell electrons and number of shells	The atomic number

Learn with Basics

Length:

Unit 1

Dalton's atomic model

Unit 2

The history of the atom

Jump Ahead

Unit 3