Topic 4 (Atomic Structure) PHYSICS

Question 1

What is the plum pudding model

Answer 1

A ball of positive charge with electrons stuck in it

Question 2

What was Rutherfords nuclear model

Answer 2

A small positive nucleus with a cloud of negative electrons. Most of the atom was empty space

Question 3

What was Bohr’s nuclear model

Answer 3

It suggested that there was still a small positive nucleus, but the electrons surrounding it, orbited in rings

Question 4

Number protons equals what

Answer 4

Number electrons

Question 5

What is an isotope

Answer 5

An isotope is a different form of the same element they have the same number of protons but a different number of neutrons

Question 6

What are alpha particles

Answer 6

Alpha particles are helium nuclei. They get stopped by a few cm of air but they are highly ionising

Question 7

What are beta particles

Answer 7

Beta particles are fast moving electrons.
They get stopped by thin sheets of aluminium (5mm) and they are moderately ionising.

Question 8

What are gamma rays

Answer 8

Waves of electromagnetic radiation they travel long distances in the air they are weakly ionising compared with alpha and beta particles. They are absorbed by thick sheets of lead or concrete walls (3+ metres)

Question 9

What is the mass number for an alpha particle

Answer 9

4

Question 10

What is the mass number for a beta particle

Answer 10

0

Question 11

What is the atomic number for an alpha particle

Answer 11

4

Question 12

What is the atomic number for a beta particle

Answer 12

-1

Question 13

What is a half life

Answer 13

The amount of time it takes for the number of radioactive nuclei in an isotope to halve

Question 14

How can gamma rays be used in the medical world

Answer 14

Since gamma rays are weakly ionising and have extremely short half life’s they can be used to kill the cancer cells whilst not damaging normal cells. However sometimes if to much radiation enters the body it can lead to mutant cells which divide uncontrollably which is just more cancer. This is why every medical situation has to look at risks and rewards

Question 15

What is nuclear fission

Answer 15

Nuclear fission is the splitting of large unstable nuclei to release energy. When a neutron is shot into an unstable atom it is absorbed, this large nucleus then splits releasing two or three more neutrons which are absorbed by other unstable atoms. This causes a large chain reaction

Question 16

What is nuclear fusion

Answer 16

Nuclear fusion is the joining of small nuclei, two light nuclei collide at high speed and join to create a larger heavier nucleus. The larger nucleus has less mass than the two separate lighter nuclei did. Some of the mass is converted to energy and released. Nuclear fusion releases a lot of energy however reactors are extremely hard and expensive to build as high temperature and pressure is needed.