When an alpha particle, which consists of two protons and two neutrons, is headed directly towards the nucleus of an atom, it does not make physical contact with the nucleus due to a phenomenon known as quantum tunneling.
Quantum tunneling is a quantum mechanical effect that allows particles to "tunnel" through potential energy barriers that would normally be insurmountable according to classical physics. In classical physics, a particle would need sufficient energy to overcome a potential barrier. However, in quantum mechanics, particles can exhibit wave-like properties and have a probability of existing in regions that are classically forbidden.
In the case of an alpha particle approaching the nucleus of an atom, there is a repulsive electrostatic force between the positively charged alpha particle and the positively charged protons in the nucleus. According to classical physics, the alpha particle would need to possess enough kinetic energy to overcome this electrostatic repulsion and physically interact with the nucleus.
However, due to the wave-like nature of particles in quantum mechanics, there is a finite probability that the alpha particle can tunnel through the potential barrier created by the electrostatic repulsion and appear on the other side without making direct physical contact with the nucleus. This probability depends on factors such as the energy of the alpha particle and the width and shape of the potential barrier.
Quantum tunneling is a fundamental aspect of quantum mechanics and plays a significant role in various phenomena, including nuclear decay, electron tunneling in electronic devices, and more.