How to Find a Quantum Number

Determining quantum numbers can be done with a Periodic Table.
••• Jupiterimages/ Images

Each element has a set of four quantum numbers that describes the energy, shape, orientation in space and spin of its electrons. These numbers are found by solving Schroedinger's equation and solving them for specific wave functions, also known as atomic orbitals. There is an easy way to find the individual quantum numbers for elements simply by using the periodic table. The table is set up like a grid, with the vertical being periods and the horizontal the groups. Quantum numbers are found using the periods of the chart.

    Look at the Periodic Table of Elements and find the element that you want to know the quantum number for. Find the principal number, which denotes the element's energy, by looking in which period the element is found. For example, sodium is in the third period of the table, so its principal quantum number is 3.

    Denote the principal quantum number as n and the second number, shape, is anywhere from 0 to n-1. So for sodium, the second quantum numbers are 0,1 and 2. Since this number represents the shape of a single electron in the orbital, the second quantum number for the element can include 0,1 and 2 depending on the electron in question.

    Call the second quantum number l. Represent the magnetic quantum number that denotes orientation of the electron in space by -l to +l. For for the case of sodium, that could be -2, -1, 0,1 and 2, if the second quantum number was 2.

    Consider the rotation of the electron like a clock. The only directions they can rotate is clockwise or counterclockwise, represented by -1/2 or +1/2. These are the only values available for the fourth quantum number.


    • The Pauli Exclusion Principle states that no two electrons within an element can have the same quantum number. Every variation of the possible quantum numbers are represented.

Related Articles

What Does the Period Number Represent?
Why Is Copper Sulfate Blue?
How Are Electrons Distributed in an Atom's Shell?
How to Determine the Valence Orbital of an Element
What Is a Noble Gas Configuration?
What Determines the Chemical Behavior of an Atom?
How to Write the Shorthand Electron Configuration for...
How to Figure Valence of Electrons in the Periodic...
How to Do Bohr Diagrams
How to Make a 3D Model of Sodium
How to Calculate the First Ionization Energy of the...
How to Find the Number of Orbitals in Each Energy Level
Examples of Elements Without a Stable Electron Configuration
How to Do Orbital Diagrams
Non Neutral Atoms Examples
How to Calculate Valency
How to Know If an Element Has a Positive or Negative...
Describe the Four Quantum Numbers Used to Characterize...
How to Calculate a Balmer Series Wavelength
How to Figure Out the Chemical Symbol for Ions

Dont Go!

We Have More Great Sciencing Articles!