It is impossible to determine simultaneously the exact position and momentum of a particle.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
The product of the uncertainties in position and momentum of a particle is at least h / 4 pi, so the more precisely one is known, the less precisely the other can be known. This limit is a fundamental property of nature and not a flaw in measuring instruments. A similar relation holds for energy and time. It means that electrons have no definite orbits, only probability distributions. The principle has direct consequences for the size and energy of atoms, because confining an electron to a small region raises its kinetic energy.
Key ideas: Position and momentum cannot both be known precisely: delta x x delta p is at least h / (4 pi), with h / 4 pi = 5.27 x 10^-35 J s. Solve for delta x = h / (4 pi m delta v). For an electron with delta v = 10^5 m per s, delta x is about 0.58 nm, bigger than an atom, so orbits are meaningless.
Common mistakes and connections: Students attribute it to measuring instruments disturbing the particle; it is a fundamental property of matter waves. It is negligible for large objects. It supports the idea of orbitals as probability regions and explains zero-point energy.
A narrow position distribution means a broad spread in momentum: the more precisely an electron is located, the less precisely its momentum is known. The interactive lesson shows this as a live animation or chart.
Locating an electron to within 1.0 x 10^-11 m makes its speed uncertain by at least about 6 x 10^6 m/s.
It is impossible to determine simultaneously the exact position and momentum of a particle.
Heisenberg Uncertainty Principle is a intermediate topic in Atomic Structure & Periodicity. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Atomic Structure & Periodicity first: Bohr Energy Levels, Limitations of Bohr Model, de Broglie Hypothesis.
The next topics in Atomic Structure & Periodicity are Wave Function and Schrodinger Equation.
Yes. The interactive lesson includes a self-check question on Heisenberg Uncertainty Principle, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Heisenberg Uncertainty Principle is topic 49 of 115 in Atomic Structure & Periodicity.