Electrons are elementary particles with a rest mass of approximately 9.1 x 10^-31 kilograms. However, it's important to note that describing the density and volume of fundamental particles, such as electrons, is not straightforward because they do not possess well-defined boundaries or spatial extents like macroscopic objects.
In the framework of quantum mechanics, electrons are described by wave functions, which represent the probability distribution of finding an electron at different locations in space. These wave functions are characterized by properties such as amplitude and phase. The square of the amplitude of the wave function gives the probability density of finding the electron at a particular location.
Due to the wave-particle duality of quantum mechanics, electrons can exhibit both particle-like and wave-like behavior. This means that while electrons can exhibit localized behavior when interacting or being measured, their wave-like nature implies that they can also exhibit characteristics of waves spread out over space.
As a result, it is not meaningful to assign a precise volume or density to an electron. The concept of volume, which is commonly associated with macroscopic objects, assumes a well-defined boundary, which is not applicable to fundamental particles. Similarly, density, which is the mass per unit volume, cannot be determined for an electron.
In summary, the description of the density and volume of an electron is not applicable in the same way it is for macroscopic objects. The properties and behaviors of electrons are best described within the framework of quantum mechanics, where they are treated as wave-like entities with probabilistic distributions in space.