Quantum mechanics is a fundamental theory in physics that describes the behavior of particles at the atomic and subatomic level. It provides a framework for understanding the peculiar behavior of electrons in atoms. One of the key concepts in quantum mechanics is wave-particle duality, which states that particles like electrons can exhibit both wave-like and particle-like properties.

Wave-particle duality can be illustrated through the famous double-slit experiment. When a beam of electrons is fired at a barrier with two small slits, an interference pattern similar to that observed with light waves is formed on a screen behind the barrier. This phenomenon demonstrates that electrons have wave characteristics.

On the other hand, particle-like behavior of electrons can be observed in experiments like the photoelectric effect. When a beam of light shines on a material, electrons are ejected from it, indicating that light can behave as particles called photons. This dual behavior of electrons is an essential aspect of their nature in quantum mechanics.