Theorised particles called Quarks have mass and charge, different combination of which give properties we identify as neutrons, protons etc.
From what i remember there are 6 quarks and each is called a "flavour" and they are: Up, down;charm; strange Top; and Bottom.
As said each has differing mass and charge and there can only be stable combinations of quarks to make stable particles like Neutrons, Protons.
I remember the famous cloud chamber photo showing a spiraling trace of a particle, the original identification of Quarks. The Particle spirals as it has a charge and the force acting on it will be at 90degrees to it's motion, aka a spiral. The direction of spiral tell you what charge the Quark is.
Maybe the Wiki can tell you more than i could:
http://en.wikipedia.org/wiki/Quark
The "Youngs" double slit experiment is evidence of wave/particle duality of light, not the existence of Quarks.
De-broglie wave length refers to all matter having "a wave length" and in this respect that electrons orbit a nuclei as a standing wave or harmonic of a standing wave. This is the only way a electron orbit could stay stable without collapsing.