What was wrong with Rutherford's model of the atom?

Rutherford's model of the atom described a dense, heavy, positively charged nucleus surrounded by negative electrons that balance out the charge of the atom. He also concluded that the atom is mostly made up of empty space.

Rutherford wanted to test the accepted theory of his day proposed by JJ Thompson where the atom was considered a round mass made of negative and positive charged particles all mixed together, called a plum pudding model.

He bombarded a thin sheet of gold with positively charged particles (alpha particles were used) to see if they would pass straight through the foil as expected. However some particles bounced back from the foil or passed through at an angle (were deflected), suggesting the gold atoms were not a homogeneous mix of positive and negative.

Rutherford's model did not account for the properties of electrons. atoms seemed too stable, they were expected to collapse when electron absorbed or released energy.

Neils Bohr used Rutherford's model and theories about quantum mechanics describing electron behavior to make a model that was accepted for the better part of the 20th century. He described atoms much like Rutherford but placed electrons in layers of orbits each with a specific energy and postulated that electrons jump up to higher energy orbits and when their energy dissipates they return to their orbits.

Read more about his model and other parts of atomic theory here: http://www.britannica.com/EBchecked/topic/514258/Rutherford-atomic-model and here: http://www.pbs.org/wgbh/aso/databank/entries/dp13at.html