Why are the shells in which electrons revolve called energy levels
The shells in which electrons revolve are called energy levels because they represent the different levels or orbits of energy that electrons occupy in an atom. Electrons can only exist in specific energy levels and transition between them by gaining or losing energy. These energy levels are quantized, meaning they can only have certain discrete values.
To understand why they are called energy levels, one needs to familiarize themselves with the concept of electron configuration. The electron configuration describes the distribution of electrons in an atom's energy levels. It is determined by a set of rules and principles, such as the Aufbau principle, Hund's rule, and the Pauli exclusion principle.
The energy levels in an atom are labeled as principle quantum numbers, denoted by integers (n). The value of n represents the relative size and energy of the shell, with smaller n values corresponding to lower energy levels. The lowest energy level, closest to the nucleus, is assigned n=1, followed by n=2, n=3, and so on.
The energy of an electron in a specific energy level is also determined by its distance from the nucleus. Electrons in higher energy levels are farther from the nucleus and have more potential energy. They require more energy to be removed from the atom or to transition to a lower energy level. Conversely, when electrons move to higher energy levels, they gain energy.
In summary, the shells in which electrons revolve are called energy levels because they represent the different levels of energy that electrons can occupy within an atom. The specific energies and arrangements of electrons within these levels are responsible for the chemical and physical properties of elements.