Radioactivity + atomic structure

Question 1

Why are some nuclei unstable?

Answer 1

There is an imbalance in the forces within the nucleus

Question 2

Why do unstable nuclei emit radiation?

Answer 2

To become more stable

Question 3

What is the process of emitting radiation from an unstable nucleus into the audience?

Answer 3

Radioactive decay

Question 4

Which of the following statements is not true?

A Isotopes can be unstable because they have too many or too few neutrons

B The process of emitting particles or waves of energy from an unstable nucleus is called radioactive decay

C Scientists can predict when a nucleus will decay

D Radiation refers to the particles or waves emitted from a decaying nucleus

Answer 4

ANSWER: C

Answer A is true. The number of neutrons in a nucleus determines the stability
Answer B is true. This is a suitable description of radioactive decay
Answer D is true. Radiation is about emissions. It is different to radioactive particles
Answer C is not true
Radioactive decay is a random process
It is not possible to predict precisely when a particular nucleus will decay

Question 5

Define radioactive activity

Answer 5

The rate at which the unstable nuclei from a source of radiation decays

Question 6

What is the unit for activity?

Answer 6

Becquerels (Bq)

Question 7

What is the device used to detect radiation?

Answer 7

A Geiger-Muller tube

Question 8

What is a count-rate

Answer 8

Count-rate is the number of decays recorded each second by a detector

Question 9

A Geiger-Muller tube is used to detect radiation in a particular location. If it counts 16,000 decays in 1 hour, what is the count rate?

Answer 9

Step 1: Identify the different variables

The number of decays is 16 000
The time is 1 hour
Step 2: Determine the time period in seconds

1 hour is equal to 60 minutes, and 1 minute is equal to 60 seconds
Time period = 1 × 60 × 60 = 3600 seconds

Step 3: Divide the total counts by the time period in seconds

Counts ÷ Time period = 16 000 ÷ 3600 = 4.5

Therefore, there are 4.5 decays per second

Question 10

What are the 3 types of radiation that can be emitted?

Answer 10

Alpha
Beta
Gamma

Question 11

What is the symbol for alpha radiation?

Answer 11

α

Question 12

What is the symbol for Beta radiation?

Answer 12

β

Question 13

What is the symbol for gamma radiation?

Answer 13

γ

Question 14

What nucleus is an alpha particle the same as?

Answer 14

A Helium Nucleus
- This is because they consist of two neutrons and two protons

Question 15

What charge do alpha particles have?

Answer 15

+2
- This means they can be affected by an electric field

Question 16

What are beta particles?

Answer 16

Beta particles are fast-moving electrons

Question 17

How are beta particles produced?

Answer 17

in nuclei when a neutron changes into a proton and an electron

Question 18

What is the charge of a beta particle

Answer 18

-1

Question 19

What are gamma rays?

Answer 19

Electromagnetic waves

Question 20

What is alpha’s range in air?

Answer 20

Few cm

Question 21

What is the range of air for a beta particle

Answer 21

Few 10’s of cm

Question 22

What is gamma radiation’s range in air?

Answer 22

several metres

Question 23

What is alpha’s penetration?

Answer 23

-Stopped by paper

Question 24

What is Beta’s penetration?

Answer 24

Stopped by a few mm of aluminium

Question 25

What is Gamma's penetration?

Answer 25

Reduced by a several cm of lead

Question 26

How strong is Alpha's ionising power?

Answer 26

Very strong

Question 27

How strong is beta's ionising power

Answer 27

A little strong

Question 28

How strong is gamma's ionising power

Answer 28

weak

Question 29

what is half life

Answer 29

the time it takes for the number of nuclei of the isotopes in the sample and count rate to halve

Question 30

Alpha particles are the same as a ______ nucleus

Answer 30

helium

Question 31

structure of alpha particle

Answer 31

2 protons 2 neutrons

Question 32

What is a beta particle

Answer 32

electron ejected from the nucleus at a high speed

Question 33

Where are beta particles formed

Answer 33

nucleus when neutron changes into a proton + electron

Question 34

Which type of radiation would not be detectable outside the body?

Answer 34

alpha

Question 35

Approximately how many times smaller is a nucleus than an atom?

Answer 35

10,000

Question 36

The electrons in an atom can only orbit at specific distances from the nucleus. State what causes an electron’s distance from the nucleus to increase or decrease.

Answer 36

Increase = absorb electromagnetic radiation [1] Decrease = emit electromagnetic radiation [1]

Question 37

A teacher wears polythene gloves as a safety precaution when handling radioactive materials. The polythene gloves do not stop the teacher’s hands from being irradiated. Explain why the teacher wears polythene gloves.

Answer 37

Wearing gloves prevents transfer of any radioactive material being transferred to the teacher’s hands [1]. If they did get radioactive material on their skin, it could cause damage over a longer period [1]

Question 38

Technetium-99 used in hospitals emits gamma radiation and has a half-life of 6 hours. After treatment, hospital equipment may become contaminated. Describe the level of the hazard associated with contamination with technetium-99. You should include in your answer a description of how the level of hazard changes over time.

Answer 38

nitially there is a high level of hazard (activity initially high) [1]. The level of hazard drops to a low level quickly (drops to safe level quickly) [1] due to short half-life [1].