Why don't electrons collide among themselves

Why don't electrons collide among themselves

Because they aren't anything like billiard balls. Check out the wave nature of matter. And take a look at the Wikipedia atomic orbitals article: "The electrons do not orbit the nucleus in the sense of a planet orbiting the sun, but instead exist as standing waves".

The Heisenberg principle states that we cannot ascertain simultaneously the position or momentum of any small particle.

See this in the Wikipedia article: "It has since become clear, however, that the uncertainty principle is inherent in the properties of all wave-like systems, and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects". Don't think of an electron as something small. It isn't some speck that has a field. Instead think standing wave, standing field. The electron is field, and it doesn't end a micron from the middle. Always remember this: it's quantum field theory, not quantum point-particle theory.

However slight, is there a chance that 2 or more electrons from the same or different orbitals may collide and lose energy thereby destabilizing the atom

No. Like rmhleo said, the Pauli exclusion principle prevents this. For an analogy, think of whirlpools. They don't overlap, and they don't crash into each other like billiard balls.

or is there a way to determine that an electron never comes in proximity of another electron with enough kinetic energy to actually smash into it?

Notwithstanding the above, there are electron colliders where this does happen.

A non-quantam mechanic answer - would be

electrostatic repulsions (b/w -vely charged electrons) would prevent it and give them definite paths which don't intersect.

Even if they move with 0.3c they can't comes much nearer than 4 fm.

before E it was thought by many that the model for the Atom was one of vibrational content. For this model to work, it requires the electrons moving at near the speed of light giving the illusion of being solid.It would explain their attratcive nature for each other... they have to be creating a small virbational field that move around the atom creating wave like fields around it, hence it has a north pole and south pole, with north and south poles bonding and creating a bigger field around them. It is kind of like human relationships should be, give and take, when one gives the other is in need and takes and then the roles reverse as they vibrate. one of the problems with this model is electron eollisions... maybe all the electrons are clumping together as to not collide...a few things are for certain with this model, there has to be unison with their movement, which the electron microscope is scattering with the frequency changes it induces. But like everything harmony always wins over chaos and the electrons come back together immediately creating its vibrational content so it continues bonding.