The concept of mass and size in elementary particles such as electrons and quarks can be a bit counterintuitive. In particle physics, particles are described as point-like entities with zero size, often referred to as "point particles." This description means that they are considered to be dimensionless and do not occupy any physical space.
However, it's important to note that the mass of a particle is not directly related to its size. Mass is a measure of the amount of matter in an object or particle, while size refers to the spatial extent or volume it occupies. In the case of elementary particles, mass is a fundamental property associated with their energy and interactions, rather than a measure of their physical size.
The concept of density is typically used to describe the mass per unit volume of a material or object. Since elementary particles are considered to have zero size, attempting to calculate their density would indeed yield an infinite value. However, it is important to recognize that applying concepts like density or size to point particles is not meaningful within the framework of current particle physics theories.
It's worth noting that our understanding of particles is based on the current theories and models in physics, such as the Standard Model. However, it is possible that future scientific advancements or new theories may provide further insights into the nature of elementary particles and their properties.