What happens when elements combine to form compounds?

The correct options are b and e.

Explanation:

Thomson's model was generally known as plum pudding model which says that the electrons are distributed in an atom which is similar to the plum present in pudding.

Rutherford's model was known as the gold-foil experiment. In this experiment, he bombarded alpha particles to an atom. He thought that the particles will directly pass through the atom because it has a lot of empty space in it. But to his surprise, he found that some of the particles reflected their path and some directly reflected their way. As the alpha particles carry +2 charge and positive charges repel each other. Hence, he concluded that the atom has a positive charge which is concentrated in a small area.

Hence, the correct statements are b and e.