The movement of electrons around the nucleus is governed by the principles of quantum mechanics. According to quantum mechanics, electrons exist in quantized energy states, known as electron orbitals or energy levels, rather than following classical trajectories like planets orbiting the Sun.
The Bohr model, proposed by Niels Bohr in 1913, was an early attempt to explain the behavior of electrons in atoms. It suggested that electrons occupy specific circular orbits at fixed distances from the nucleus, similar to planets orbiting the Sun. These orbits were called "Bohr's orbits." However, this model had limitations and was later superseded by a more accurate description provided by quantum mechanics.
In quantum mechanics, the behavior of electrons is described by wave functions, which represent the probability distribution of finding an electron in a particular region around the nucleus. These wave functions are associated with specific energy levels, and each energy level can accommodate a certain number of electrons.
The concept of electron orbitals emerged from the application of quantum mechanics to the behavior of electrons in atoms. Electron orbitals are three-dimensional regions of space where the probability of finding an electron is high. Each electron orbital is associated with a specific energy level and has a characteristic shape, such as spheres, dumbbells, or more complex shapes.
The allowed electron orbitals are determined by the quantum numbers associated with the electron, such as the principal quantum number, angular momentum quantum number, magnetic quantum number, and spin quantum number. These quantum numbers define the energy, shape, and orientation of the electron orbitals.
Outside the region defined by the allowed electron orbitals for a particular atom, the probability of finding an electron becomes extremely low. This is due to the quantum mechanical nature of electrons and the specific quantization of their energy levels.
In summary, electrons move around the nucleus in specific electron orbitals or energy levels, as described by quantum mechanics. The concept of "Bohr's orbits" was a simplified model that provided a useful starting point for understanding atomic structure but was later refined through quantum mechanics.