Take the model of an atom...the nucleus with the electron orbiting around it at near light speed in all directions.take our solar system,what is it that keeps the earth from falling into the sun?it's the velocity of the earths orbit.if the earth slows down it will fall closer to the sun.but since the speed of light/electrons is constant the electron can never fall into the nucleus.the attraction of the nucleus and speed of the electron are mutual to the end product:atom.matter is the result of a compromise between a minute attraction and a constant speed.the electron is simply as close as possible without slowing down.so you have attraction,velocity and repulsion(the minimum radius of the orbit).the weight of the electron has no effect because being in an "omniorbit" it cancels itself out.as far as covalent bonds are concerned the electron is effectively changing directions affected by another nucleus and doesn't necessarily "know" it is being shared.any thoughts are welcomed.feel free to expand on this.