Electron Configuration tells you the location that an electron "lives" at in an atom

• There are four types of sublevels or orbital shapes

• S, p, d, & f

The orbital shapes can be described as the path that the electron takes around the nucleus.

• There is:

• 1 s orbital

• 3 p orbitals

• 5 d orbitals

• 7 f orbitals

Each orbital can contain up to 2 electrons

• s orbitals can hold a total of 2 electrons (1 orbital)

• p orbitals can hold a total of 6 electrons (3 orbitals)

• d orbitals can hold a total of 10 electrons (5 orbitals)

• f orbitals can hold a total of 14 electrons (7 orbitals)

The blocks of the periodic table

As you can see here the "s" block is shown on the left in pink, the "p" block is on the right in orange, the "d" block is in the middle shown in blue, and the "f" block is shown below in yellow.

Columns on the periodic table and the orbitals...

• The s block contains 2 columns

• The p block contains 6 columns

• The d block contains 10 columns

• The f block contains 14 columns

Think about it....

The s block contains 2 columns and the "s" orbitals can contain 2 electrons. The p block contains 6 columns and the "p" orbitals can contain up to 6 electrons. The d block contains 10 columns and the the "d" orbitals can contain up to 10 electrons! (This is NOT a coincidence!)

Orbital filling

Electrons fill these orbitals in a way that allows them to take the easiest root possible. The LOWEST energy levels are filled first.

Orbital filling cheat sheet

By following the arrows you can easily find out the proper electron configuration levels.


This is the EXACT same thing as following the periodic table one element at a time.

USE WHATEVER IS EASIER FOR YOU

You can show an electrons address in two ways: an orbital diagram or an electron configuration

Orbital shapes

As you can see, the s orbital is a circular path around the nucleus and that is why there is only one option. The p orbital is a figure-8 path that can be on the x-axis, the y-axis, or the z-axis in a 3-D atom. This is why there are 3 different p orbitals.

Orbital Diagrams = arrows chart with sublevels and orbitals listed


Electron Configuration = Letters and numbers only = 1s2 2s2 2p6....

Lets start with orbital diagrams!


To start - remember the rules

Aufbau Principle

states that electrons fill lower-energy atomic orbitals before filling higher-energy ones (Aufbau is German for "building-up")

Pauli Exclusion Principle

No two electrons in the same atom can have identical values for all four of their quantum numbers.

In other words:

(1) no more than two electrons can occupy the same orbital

(2) two electrons in the same orbital must have opposite spins 

Hunds Rule

every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.

How to Write an Electron Configuration:

1. Start with the shell/period number

2. Followed by the type of orbital

3. Finally the superscript indicates the number of electrons in the orbital

Example: B = 1s² 2s² 2p¹

• Noble gasses are the last column of the periodic table

• They are less reactive than any other atoms on the periodic table because their final orbital is filled

Noble Gases

• Shortcut (use the last noble gas)

Noble Gas Configuration

​Core Electrons – go up one energy level and over to the noble gas

To create a valence electron configuration

1. Find the highest level your element is in

2. Give only the s or the s +p if it is available

Example: Nitrogen

Nitrogen is in energy level 2 so it should be 1s2 2s2 2p3

Valence configuration would only be 2s2 2p3