What is discrete energy in atomic physics?

Discrete energy in atomic physics refers to the specific, fixed energy levels that electrons can occupy within an atom.

In more detail, the concept of discrete energy is a fundamental principle in quantum mechanics, which is the branch of physics that deals with phenomena on a very small scale, such as atoms and subatomic particles. According to quantum mechanics, the energy of an electron in an atom is quantised, meaning it can only take on certain specific values. These values correspond to the different energy levels or 'shells' within the atom. For a deeper understanding of these concepts, exploring the atomic energy levels can provide additional insights.

This is a departure from classical physics, which predicts that electrons should be able to exist at any energy level. However, experiments such as the photoelectric effect and atomic emission spectra have provided evidence for the existence of discrete energy levels. For example, when atoms are heated or otherwise excited, they emit light at specific wavelengths. These wavelengths correspond to the energy differences between the discrete levels, providing a kind of 'fingerprint' for each type of atom. The photoelectric effect is a classic experiment that supports the quantisation of energy.

The concept of discrete energy also explains why atoms are stable. According to classical physics, electrons orbiting the nucleus should continuously lose energy and spiral into the nucleus, causing the atom to collapse. However, in quantum mechanics, an electron in a particular energy level is stable and will not lose energy unless it is perturbed.

The energy levels are often depicted as concentric circles around the nucleus in diagrams, but it's important to remember that this is a simplification. In reality, the energy levels correspond to different shapes of electron cloud, or 'orbitals', which are regions of space where the electron is likely to be found. These orbitals have different shapes and orientations depending on the energy level and other quantum numbers. The diverse types of waves encountered in physics further illustrate the variety of ways energy can be manifested.

In summary, discrete energy in atomic physics refers to the specific, quantised energy levels that electrons can occupy within an atom. This concept is a key part of quantum mechanics and is supported by experimental evidence. An advanced understanding of how these energy levels contribute to the Bohr model can be gained by studying the energy levels in the Bohr model.