Describe the main difference between the bohr model of the atom and the rutherford model.

To put this as straight forward as possible, Rutherford came up with the nuclear model of the atom, before that, no one knew that the nucleus even existed, people use to think that most of the atom was made up of positive charge overall, with some negative (electrons) charge on the top of it, this theory was called the Plum pudding.

Rutherford disproved this theory, and came up with his own model, which would contain the nucleus, in this there's a tiny positively charged nucleus at the centre, surrounded by a cloud of negative electrons . 
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Bohr modified the atom structure even more, he realised that electrons in a cloud around the nucleus of an atom, as Rutherford described would quickly spiral down into the nucleus, causing the atom to collapse. So Bohr proposed a new model of the atom with basic principals:

-Electrons only exist in fixed orbitals (shells) and not anywhere in between.
-Each shell has a fixed energy

Rutherford explained the nucleus of an atom, while Bohr was more into the electrons and their energy levels.

hope that helps

In the Rutherford model, electrons can exist in any location outside the nucleus.

In the Bohr model, electrons can exist only in certain energy levels surrounding the atom.

the answer is d.) potassium