Electrons are elementary particles that are fundamental to many scientific principles, including atomic and molecular structure, chemical bonding, and the behavior of electricity. They are negatively charged and have a mass much smaller than protons and neutrons. Electrons exist in orbitals surrounding the nucleus of an atom, and their specific arrangement in these orbitals determines many of the atom’s properties, including its chemical behavior and the nature of its bonding with other atoms. Electrons can also be excited to higher energy levels, resulting in phenomena such as the emission of light in chemical reactions and the operation of electrical devices.