Are Particles Theoretically Tangible?

[Jehanne]

Last I read is that an isolated quark has never been observed.

From what I remember, protons and neutrons are made of different combinations of three quarks. But an electron, is basically the size of one quark.

An electron (at least a bound one) is a wave as well as a particle; it is problematic to speak of its size. Ditto for quarks, which, from my understanding, have most of their mass in the nuclear fields that bind them together. Such is the realm of QCD, the complex theories that describe the nuclei of atoms.

A great book on all of this is Modern Physics by Professor Kenneth Krane, a sophomore level undergraduate physics textbook; many other similar texts are also available.