Now it is possible to see a movie of an electron. Previously it has been impossible to photograph electrons since their extremely high velocities have produced blurry pictures. In order to capture these rapid events, extremely short flashes of light are necessary, but such flashes were not previously available.

Protons and Electrons A proton carries a positive charge (+) and an electron carries a negative charge (-), so the atoms of elements are neutral, all the positive charges canceling out all the negative charges. Atoms differ from one another in the number of protons, neutrons and electrons they contain.

Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms.

Quarks

And since the electron is the lightest particle that has electric charge, there is nothing that it can decay to; only neutrinos, photons, gluons and gravitons are lighter, but they are all electrically neutral, so any combination of them would have zero electric charge.

Anode ray

A tiny number of alpha particles, traveling at 10% of the speed of light, hit a dense atomic center right in its middle. The collision and the repulsion cause the alpha particle to “bounce” backwards and move on a very different path. These are the reflected rays.

Ernest Rutherford carried out an experiment to investigate the structure of the atom. He fired alpha particles at a thin gold foil, and observed the path of the alpha particles. The whole apparatus was in a vacuum chamber.

Surprisingly, while most of the alpha particles were indeed undeflected, a very small percentage (about 1 in 8000 particles) bounced off the gold foil at very large angles. Some were even redirected back toward the source. No prior knowledge had prepared them for this discovery.

c) Few α – particle after striking the gold foil retrace their path shows that the positively charged centre was concentrated in a very small volume of space and was called nucleus.