MODULE 8: Universe to the atom

Question 1

Explain how mass defect relates to atoms

Answer 1

The mass defect of a nucleus is the difference between the total mass of a nucleus and the sum of the masses of all its nucleons.

Question 2

Explain how binding energy relates to atoms

Answer 2

The binding energy of a nucleus is equal to the amount of energy released in forming the nucleus, or the mass defect multiplied by the speed of light squared (E =mc2)

Question 3

Explain how the Bohr model overcomes an identified limitation of the Rutherford model

Answer 3

By introducing the idea of stable and quantised atomic energy levels Bohr was able to overcome the atomic instability of Rutherford’s model by proposing laws of electromagnetism do not apply without explaination. As orbitting electrons orbit the nucleus due to electrostic attraction of a positive nucleus, they do not lose energy and do not spiral into the nucleus and hence exist in stable and discrete energy levels and orbits surrounding the nucleus.

Question 4

Outline the key features of the Rutherford model

Answer 4

Rutherford’s planetary model consisted of empty space where electrons orbit a tiny positively charged nucleus that contained most of the mass of the atom similar to how planets orbit the sun.

Question 5

Identify the forces acting an oil drop (Milikan’s Experiment)

Answer 5

• drag force (upwards)

- weight force (downwards)