Electrons are commonly referred to as particles in the context of quantum mechanics, but their nature is somewhat more nuanced. According to quantum field theory, which is the framework that underlies our understanding of elementary particles, electrons are considered to be both particles and excitations of the electron field.
In quantum field theory, particles are described as localized excitations or quanta of their corresponding quantum fields. The electron field permeates all of space, and when it is disturbed or excited, it can manifest as an electron "particle" in certain interactions or measurements.
The electron field itself is not directly created by the nuclei. The nuclei consist of protons and neutrons, which are made up of quarks held together by the strong nuclear force. Electrons, on the other hand, are fundamental particles that are not composed of smaller constituents.
The electron field exists independently of the nuclei and interacts with them through electromagnetic forces. Electrons can be bound to the positively charged nuclei of atoms, forming an atom's electron cloud or electronic structure. In this context, the interaction between the electron field and the positively charged nuclei determines the behavior and properties of electrons in atoms.
So, while electrons can be thought of as both particles and excitations of the electron field, the creation of electron excitations does not arise directly from the nuclei but rather from interactions involving the electron field and its dynamics.