2·The Atomic Structure excerpt talked about Rutherford\'s experiments firing alp

Question

2·The Atomic Structure excerpt talked about Rutherford's experiments firing alpha particles at thin sheets of gold foil. a) Explain why Thompson's model of the atom would have resulted in the alpha particles having very small deflections as they pass through the gold atoms. the gold nucleus rather than by the electrons orbiting the nucleus other scientists prior to Rutherford's observation of large deflection angles. b) Explain why in Rutherford's model of the atom the alpha particles are affected primarily by c) Explain two reasons why Rutherford's model of the atom was not obvious to Thompson or

Explanation / Answer

a) Thompson's atomic model is called the plum pudding model because he thought the spherical atom was made up of positively charged filling and electrons are scattered inside the atom like plums in the pudding. Since in the model, the positive charge is uniform everywhere inside the sphere, the positively chatged alpha particles when bombarded on the atom will have very small deflection and the alpha particles would have passed through in a straight line.

b) In Rutherford's model, most of the atom is empty. The central core has small positively charged nucleus and the electrons orbit around the nucleus like planets orbit around the Sun. The electron's have very small mass and are extremely tiny compared to alpha particles. Hence the orbiting electrons don't have any effect on the alpha particles. On the other hand, the central nucleus is very dense and have comparable mass and size to the alpha particles. Aso since the nucleus and alpha particles are both positively charged, the alpha particles are deflected away from the nucleus.

c)

i) Thompson in his famous experiment had found in 1896 that the cathode rays found in cathode ray tubes were deflected by electric and magnetic fields just as if they were tiny little lumps of electrically charged matter. Which is why he came up with the plum pudding model. The fact that electrons can orbit around the nucleus never occurred to him.

ii) Before Thompson, John Dalton had an idea of the atom. From his experiments and observations, he came to the conclusion that atoms are like tiny, hard balls and could not be split.

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