Basically, one of the implications of Heisenberg's uncertainty principle is that the more accurate the measurement of position, the less accurate the measurement of momentum and vice versa. Hence on the subatomic scale, the traditional system of orbiting electrons is no longer correct, as it presumes each electron has an exact position and velocity. The solutions is that the position of the electron is no longer expressed as an exact object, but as an equation giving the probability of the electron being in a certain place at the time. To visualise this, is it better to see the electrons as a cloud of charge around the atom.
Originally posted by RuroumiKenshin What is an electron cloud?
FZ+ may have told you a little more than you wanted to know, but the term is by Neils Bohr (i believe!) and it has to do with discribing the behavior of electrons as the magnetically orbit their magnetically opposite particle, the proton in the nucleus (got it?). the term cloud is a strange one because its impossible to see what it looks like down there but i guess that's what mr. bohr thought it would! basically FZ+ is right though, it is a bit out dated.