Atomic Theory Chem (DH) Practice Test

The Heisenberg Uncertainty Principle asserts that it is fundamentally impossible to know both the exact position and momentum (which includes velocity) of a particle, such as an electron, simultaneously. The correct reasoning centers on the nature of measurement in quantum mechanics.

When measuring an electron’s position, a photon or another particle is often used to determine that position. The interaction required to "see" or measure the electron disrupts its velocity due to the impact of the photon's momentum. This interaction causes a change in either its position or momentum, meaning that the very act of measuring one of these properties introduces uncertainty into the other. Thus, due to the reliance on photons (or other particles) for measurement, knowing both properties at the same time becomes impossible.

This principle is a cornerstone of quantum mechanics and highlights the limitations inherent in observational technology at the quantum scale, differing from classical physics where it may be possible to measure both position and velocity with arbitrary precision.