Q 7 d) What is Thomson's plum pudding model? Answer: Thomson knew that atoms had an overall neutral charge. Therefore, he reasoned that there must be a source of positive charge within the atom to counterbalance the negative charge on the electrons. This led Thomson to propose that atoms could be described as negative particles floating within a soup of diffuse positive charge. This model is often called the plum pudding model of the atom, due to the fact that its description is very similar to plum pudding, a popular English dessert (see image below). Q- 8 a) Explain the discovery of electrons. Ans: What are Electrons? Electrons are subatomic particles that hold an elementary charge of magnitude -1. The charge of an electron is equal in magnitude to the charge held by a proton (but has an opposite sign). Therefore, electrically neutral atoms/molecules must have an equal number of electrons and protons. Although the magnitude of the charges held by protons and electrons are ...