Electrons in an atom do not actually orbit the nucleus in the way that planets orbit the sun. The behavior of electrons in atoms is better described by quantum mechanics, which introduces the concept of electron orbitals or electron probability clouds.
In quantum mechanics, electrons are considered to exist in specific energy levels or shells around the nucleus. Each energy level can contain a certain number of electrons. The energy levels are further divided into sublevels or orbitals, which have different shapes and orientations within the energy level.
The distribution of electrons in these orbitals is determined by their energy and the principle of electron configuration. The lowest energy level, called the 1s orbital, is closest to the nucleus and can hold up to two electrons. The next energy level, 2s, can also hold up to two electrons, and so on.
The behavior of electrons is governed by a set of principles, including the Pauli exclusion principle, which states that no two electrons in an atom can have the same set of quantum numbers. This principle leads to the filling of orbitals in a specific order, known as the aufbau principle.
The orbitals that hold electrons are characterized by their shape, size, and orientation in space. There are various types of orbitals, such as s, p, d, and f orbitals, each with a distinct shape and number of suborbitals.
Some orbitals are considered more stable or better for holding electrons than others. This stability arises from the distribution of electron density and the balance of attractive and repulsive forces within the atom. Specifically, orbitals that have a spherical shape, such as the 1s orbital, have a more symmetric distribution of electron density and are more stable. Orbitals with higher energy and more complex shapes, such as the d and f orbitals, are less stable.
The concept of electron orbitals provides a more accurate description of the behavior of electrons in atoms compared to the classical idea of orbits. Electrons are not confined to specific paths around the nucleus but exist in regions of space with higher probabilities of finding them. The distribution of electrons in orbitals determines the chemical and physical properties of elements and their interactions with other atoms.