Question

What's the Pauli-exclusion Principle?

Asked by: Wolfgang M.

Answer

In 1925, Wolfgang Pauli gave physics his exclusion principle as a way to explain the arrangement of electrons in an atom. His hypothesis was that only one electron can occupy a give quantum state. That is, each electron in an atom has a unique set of quantum numbers (the principle quantum number which gives its energy level, the magnetic quantum number which gives the direction of orbital angular momentum, and the spin quantum number which gives the direction of its spin). If this principle did not hold, all of the electrons in an atom would pile up in the lowest energy state (the K shell). In fact, we now know that that the Pauli exclusion principle holds for not just electrons but for any fermions (half-integer spin particles like electrons, protons, neutrons, muons, and many more.)

Answered by: Joseph Kozminski, B.S., Physics Grad Student, MSU, East Lansing, MI

Search

Loading






Science Quote

'An expert is someone who knows some of the worst mistakes that can be made in his subject and how to avoid them.'

Werner Heisenberg
(1901-1976)
Science Sidebar | Science Education Articles
Cool Summer Science Projects

Why not make science a part of your family’s summer? Perhaps you can set aside one day a week for outdoor projects—maybe Mad Scientist Monday or Scientific Saturday? Here are a few ideas to help get you started. Continue reading ...

10 Ways to Keep Your Kids Interested In Science

Young children are natural scientists: they ask questions, pick up sticks and bugs outside, and are curious about the world around them. But as they get a bit older, many kids gradually lose their interest in science. They might see it as just another task at school, something that doesn't apply to their lives. Of course nothing could be further from the truth, so here are ten ways you can remind your kids that science is everywhere. Most of these are fun for adults, too! Continue reading ...

Top Selling

Here are our physics & astronomy bestsellers:
Magnetic Levitator - Classic
3D Magnetic Field Tube
KonusScience 5 Way Microscope Kit
Periscope
Revolving Multi-Color Fiberoptic Light
Tin Can Robot 4M Kit
Potato Clock 4M Kit
Mini Plasma Ball
Clean Water Science 4M Kit
Top Secret - Spinning Top

Sponsors

USC University of Southern California Dornsife College Physics and Astronomy Department McMaster University Physics and Astronomy Department