According to the laws of classical physics, electrons should be attracted to the positively charged nucleus and eventually collide with it, causing atoms to collapse. However, in the quantum mechanical model of the atom, electrons are described as existing in orbitals or energy levels around the nucleus, and these orbitals have a specific energy that prevents the electrons from falling into the nucleus.
The concept of quantized energy levels in the quantum mechanical model explains why electrons do not fall into the nucleus. These energy levels act as barriers, preventing the electrons from getting too close to the nucleus and experiencing a strong attractive force.
Electrons stay in orbit around the nucleus due to the balance of two opposing forces - the electrostatic attraction between the positively charged nucleus and negatively charged electrons, and the centrifugal force caused by the electron's motion. This balance of forces allows the electron to maintain a stable orbit around the nucleus.
In rare cases, electrons can transition to lower energy levels, which may bring them closer to the nucleus. However, they do not fall into the nucleus due to the energy barrier and the repulsive force between like charges. Additionally, electrons can also be ejected from the atom if they gain enough energy.
The discrete energy levels of electrons in atoms are a result of the wave-like nature of particles on the atomic scale. The energy levels correspond to the different wavelengths of the electron's wave function, and only certain wavelengths are allowed, leading to discrete energy levels. This is a fundamental aspect of the quantum mechanical model of the atom.