MCAT Content / Electronic Structure / Heisenberg Uncertainty Principle

Heisenberg Uncertainty Principle

Topic: Electronic Structure

The Heisenberg Uncertainty Principle states that it is impossible to determine both the position and the velocity of an electron simultaneously

The detection of an electron, for example, would be made by way of its interaction with photons of light. The observation of an electron with a microscope requires reflection of a photon off of the electron. This reflected photon causes a change in the path of the electron. Since photons and electrons have nearly the same energy, any attempt to locate an electron with a photon will knock the electron off course, resulting in uncertainty about where the electron is located.

We do not have to worry about the uncertainty principle with large everyday objects because of their mass. They behave much more like particles rather than waves. If you are looking for something with a flashlight, the photons coming from the flashlight are not going to cause the thing you are looking for to move. This is not the case with atomic-sized particles, leading scientists to a new understanding about how to envision the location of the electrons within atoms.


Key Points

• The Heisenberg Uncertainty Principle states that it is impossible to determine both the position and the velocity of an object simultaneously.


Key Terms

photon: the smallest discrete amount of electromagnetic radiation. It is the basic unit of all light, carrying the energy E= hf.

electron: each electron has a negative charge (-1) with weight so small it’s normally negligible as compared to proton or neutron.

Heisenberg Uncertainty Principle: It is impossible to determine both the position and the velocity of a particle simultaneously.



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