topic 4 - atomic structure: atoms and nuclear radiation

Question 1

What happens with the nucleus of an atom when it tries to become more stable?

Answer 1

It gives out radiation in a process called radioactive decay.

Question 2

What is radioactive decay?

Answer 2

A random process in which a nucleus gives out atomic radiation to become more stable?

Question 3

Do stable or unstable atoms give out radioactive decay?

Answer 3

Unstable atoms.

Question 4

What is activity?

Answer 4

The rate at which a source of unstable nuclei decays.

Question 5

What is activity measured in?

Answer 5

Becquerel (Bq).

Question 6

What is count rate?

Answer 6

The number of decays recorded each second by a detector.

Question 7

Give an example of a detector used to measure count rate.

Answer 7

A Geiger-Muller tube.

Question 8

What are the 4 types of ionising radiation which can be released from a nucleus?

Answer 8

• Alpha
• Beta
• Gamma
• Neutron

Question 9

What is ionising radiation?

Answer 9

Radiation which knocks electrons off atoms.

Question 10

What does ionising radiation create.

Answer 10

Positively charged ions.

Question 11

What does the ‘ionising power’ of a radiation source mean?

Answer 11

How easily is can perform ionising radiation.

Question 12

What is the symbol for an alpha particle/

Answer 12

α

Question 13

What are alpha particles made up of?

Answer 13

2 protons and 2 neutrons.

Question 14

What element has the same nucleus as an alpha particle?

Answer 14

Helium.

Question 15

What is the penetration through materials of alpha particles like?

Answer 15

Don’t penetrate very far into materials and are stopped quickly - they are absorbed into a sheet of paper.

Question 16

What is the range of alpha particles in air?

Answer 16

A few cm.

Question 17

What is the ionising power of alpha particles like?

Answer 17

Strongly ionising.

Question 18

Give a practical use of alpha particles.

Answer 18

Smoke detectors

Question 19

How do alpha particles work in smoke detectors?

Answer 19

Smoke detectors ionise air particles, causing a current to flow. If there is smoke in the air, it binds to the ions, meaning the current stops and the alarm sounds.

Question 20

What is the symbol for a beta particle?

Answer 20

β

Question 21

What is a beta particle made up of?

Answer 21

A high-speed electron ejected from the nucleus as a neutron turns into a proton.

Question 22

What is the mass of a beta particle?

Answer 22

Virtually none.

Question 23

What is the charge of a beta particle?

Answer 23

-1

Question 24

What is the penetration through materials of beta particles like?

Answer 24

They penetrate moderately far before colliding.

Question 25

What is the range of beta particles in air?

Answer 25

A few metres.

Question 26

What material can be used to absorb beta particles?

Answer 26

A sheet of aluminium.

Question 27

How ionising are beta particles?

Answer 27

Moderately ionising.

Question 28

Give a use of beta particles.

Answer 28

Testing the thickness of sheets of metal.

Question 29

What is the symbol for gamma rays?

Answer 29

γ

Question 30

What is a gamma ray made up of?

Answer 30

Electromagnetic radiation from the nucleus.

Question 31

What is the pentration through materials of gamma rays like?

Answer 31

Penetrate far into materials without being stopped.

Question 32

How far can gamma particles travel through air?

Answer 32

A long distance.

Question 33

How ionising are gamma particles?

Answer 33

Weakly ionising.

Question 34

What can gamma particles be absorbed by?

Answer 34

Thick sheets of lead or metres of concrete.

Question 35

What are nuclear equations used to represent?

Answer 35

Radioactive decay.

Question 36

In nuclear equations, what symbol may an alpha particle be represented by?

Answer 36

He (mass no.=4, atomic no.=2)

Question 37

In nuclear equations, what symbol may a beta particle be represented by?

Answer 37

e (mass no.=0, atomic no.=-1)

Question 38

What is the general form of a nuclear equation?

Answer 38

atom before decay –> atom after decay + radiation emitted

Question 39

What must be equal on both sides of a nuclear equation?

Answer 39

The total mass and atomic numbers.

Question 40

How does alpha decay change the charge and mass of the nucleus?

Answer 40

It decreases both the charge and mass.

Question 41

How does beta decay affect the charge of a nucleus?

Answer 41

It increases the charge.

Question 42

How does the emission of a gamma ray affect the mass and charge of a nucleus?

Answer 42

It doesn’t affect it.

Question 43

Is radioactive decay predictable or random?

Answer 43

Random.

Question 44

What is the half life of a radioactive isotope?

Answer 44

The time it takes for the number of nuclei in a sample of the isotope to halve.
OR
The time it takes for the count rate from a sample containing the isotope to fall to half its initial level.

Question 45

What half-life be used to find?

Answer 45

The rate at which a source decays (its activity).

Question 46

Each time a radioactive nucleus decays to become a stable nucleus, what decreases?

Answer 46

The total activity.

Question 47

What does a short half-life mean for activity and why?

Answer 47

The activity decreases quickly because the nuclei arevert unstable and rapidly decay.

Question 48

What does a long half-life mean for activity and why?

Answer 48

The activity decreases slowly because most of the nuclei don’t decay for a long time.

Question 49

Why can sources with a short half-life be dangerous?

Answer 49

They emit a high amount of radiation at the start.

Question 50

Why can sources with a long half-life be dangerous?

Answer 50

Nearby areas are exposed to radiation for years.

Question 51

(got up to

Answer 51

radioactive contamination)