How to Calculate Electron Configuration

Use the periodic table to calculate an electron configuration.
••• Marco Hegner/iStock/Getty Images

Sometimes you need to know where electrons are likely to be in an atom. Electron configurations help you to do this. To calculate an electron configuration, divide the periodic table into sections to represent the atomic orbitals, the regions where electrons are contained. Groups one and two are the s-block, three through 12 represent the d-block, 13 to 18 are the p-block and the two rows at the bottom are the f-block. The row numbers one through seven represent the energy levels that contain the orbitals and electrons.

Writing the Configuration

Starting at the top of the periodic table and moving from left to right across the rows, write the row number, the block letter and how many squares are in each block's section until you get to the desired element. To calculate the electron configuration for phosphorus (P), which is in the third row, p-block, third element in that block, write: 1s2 2s2 2p6 3s2 3p3. Check your work by adding the electron numbers to see if they equal the atomic number of the element; for this example, you would write: 2+2+6+2+3=15, which is the atomic number of phosphorus.

Special Instructions

Because an atom's orbitals sometimes overlap in real life, you must account for that in your configurations. For the d-block, change the row number to one number less than it actually is. For example, the electron configuration for germanium (Ge) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2. Notice even though you are on row four, it is called "3d" to account for overlap.

Related Articles

Why Do Compounds of Metals & Nonmetals Consist of Ions?
How to Make a Three-Dimensional Atom Project
How to Do Bohr Diagrams
How to Determine How Many Dots Are on an Element's...
Easy Way to Remember Valences
How to Determine the Valence Orbital of an Element
How to Find the Number of Electrons
How to Do Orbital Diagrams
How to Figure Valence of Electrons in the Periodic...
How to Make a 3-D Bohr Model
How to Determine the Number of Electrons With Quantum...
How to Read the Periodic Table for Kids
How to Make a Bohr Model of the Atom
How to Draw Electron Dot Diagrams
How to Build the Atomic Structure of Helium
How to Draw a Helium Atom
How to Make a Boron Atom Model
How to Find the Number of Ions in a Compound
Differences Between Transition Metals & Inner Transition...
How to Determine How Many Hybrid Orbitals