Electrons orbit around the nucleus in specific energy levels or electron shells due to the principles of quantum mechanics. The behavior of electrons in atoms is best described by quantum theory, specifically the concept of electron wavefunctions.
According to quantum mechanics, electrons exist in a state of superposition, meaning they can occupy multiple positions or energy levels simultaneously. The electron wavefunction describes the probability distribution of finding an electron in a particular region around the nucleus.
Electrons in atoms occupy specific energy levels, which are characterized by discrete values. These energy levels correspond to different electron shells, such as the first shell (closest to the nucleus), the second shell, the third shell, and so on. Each shell can hold a limited number of electrons, and electrons fill these shells from the innermost to the outermost shells.
The reason electrons do not collide with protons is primarily due to their wave-like nature and the inherent uncertainty principle in quantum mechanics. The wavefunction of an electron describes its position and momentum, and it is subject to uncertainty. This uncertainty principle states that there is a fundamental limit to how precisely the position and momentum of a particle can be known simultaneously.
The electron's wavefunction spreads out around the nucleus, forming a probability cloud. This cloud represents the regions where the electron is most likely to be found. The distribution of electron density determines the size and shape of the electron orbitals.
In simple terms, the electron cloud is a three-dimensional region around the nucleus where the electron is most likely to exist. The orbitals within this cloud provide a probabilistic description of where the electron might be found.
Due to the wave-like nature of electrons, they do not follow classical trajectories like planets orbiting the Sun. Instead, they occupy specific regions around the nucleus, and their behavior is described by the probabilities dictated by quantum mechanics. This is why electrons do not collide with protons but instead maintain stable, quantized orbits within the electron shells.