P8

Question 1

Describe the structure of an atom

Answer 1

Nucleus -> protons and neutrons
Electrons surround nuclei

Question 2

What are the properties of electrons, protons and neutrons?

Answer 2

Proton:
Positive charge
1 amu
In nucleus

Neutron:
Neutral
1 amu
Nucleus

Electron:
Negative charge
Around 0 amu
Shells orbiting nucleus

Question 3

What define an element?

Answer 3

The number of protons it has

Number of electrons (ions) and neutrons (isotopes) can vary

Question 4

What are proton and nucleon number?

Answer 4

(Z) Proton number -> atomic number
(A) Nucleon number -> atomic mass

Question 5

What is an isotope?

Answer 5

An atom of the same element (same number of protons and electrons) that has a different mass (different number of neutrons)

Different mass
Same proton number (so same element)
No charge

Question 6

What is a nuclide?

Answer 6

A group of atoms with the same number of protons and neutrons

Question 7

What is the format of nuclide notation?

Answer 7

A (proton number)
X (element)
Z (nucleon number)

Question 8

T or F: radioactive emissions are random

Answer 8

True

Question 9

What causes an unstable nuclei?

Answer 9

Imbalanced forced within the nucleus

Due to:
Large size (more protons than may repel each other)
Too few or too many neutrons

Question 10

What is radioactive decay? How does it connect to radiation?

Answer 10

An unstable nuclei can emit radiation to become more stable
Reduces the energy -> nucleus more stable
This is radioactive decay

The radiation emitted is referred to as nuclear radiation

Question 11

What are the characteristics of alpha particles?

Answer 11

helium nucleus -> 2 protons, 2 neutron
Have charged +2
Can be affected by an electric field
Range of a few cm
Can be stopped by paper
High ionisation power

Question 12

What are the characteristics of beta particles?

Answer 12

Fast moving electron (produced in nuclei -> neutron=proton+electron)
Charge -1
Can be affected by an electric field
Range of a few 10s of cm
Stopped by few mm of aluminium
Medium ionisation power

Question 13

What are the characteristics of gamma rays?

Answer 13

Electromagnetic waves -> highest energy em waves
No charge
Range -> infinite
Reduced (not stopped) by few mm of lead
Low ionisation power

Question 14

How do alpha particles, beta particles and gamma particles react to being in a magnetic field?

Answer 14

Alpha -> curve down
Beta -> curve up quickly
Gamma -> no charge, unaffected

Particles only react if they are charged and moving perpendicular to the field

Question 15

What is ionizing radiation?

Answer 15

Radiation which results in removal of electrons from atoms or molecules

Question 16

What is the ionizing powers of alpha, beta and gamma (relatively)? Why?

Answer 16

Alpha -> most ionizing (dense trail)
Lose energy quickly, has a short range as a result

Beta -> medium ionizing (medium trail)
Loses energy less quickly, has a longer range, but more penetrating

Gamma -> low ionizing (very not dense trail)
Loses energy slowly, greater range, very penetrating

Question 17

What is a practical application of alpha particles? Why is it used instead of another type of radiation?

Answer 17

Smoke detectors

Alpha radiation ionizes air -> creates current across gap, completing a circuit (current detected by ammeter) -> smoke fills gap (smoke absorbs alpha particles) -> less or no current is picked up -> ammeter detects -> alarm

Americium-241 used as alpha source

Most ionizing
Least penetrating and doesn’t have a big range

Question 18

What is a practical application of beta particles? Why is it used instead of another type of radiation?

Answer 18

Measuring thickness
Materials wrong thickness -> amount of radiation out of range -> machine makes adjustments for constant thickness
Beta used because it is partially penetrating

Crack in pipe
Radiation cannot perpetrate the pipe
Crack -> radiation can be detected
Short half life -> doesn’t effect water supplies

Question 19

What is a practical application of gamma rays? Why is it used instead of another type of radiation?

Answer 19

Radiotherapy (treatment of cancer using radiation)
Radiation kills living cells -> cancer cells are more susceptible rays are directed and moved to minimise harm to the rest of the body

Sterilisation
Sterilize food and medical equipment

Gamma used in both because:
Most perpetrating

Question 20

What is background radiation?

Answer 20

Radiations that exist around us at all times

Usually just natural radiation, but human activity has increased it

Question 21

What are the 2 types of background radiation? Give some examples.

Answer 21

Natural: rocks (radon gas (alpha radiation) -> granite or uranium in rocks) , cosmic rays (high speed protons from sun collide with air molecules) , food (usually contact with rocks)

Man made: medical X-rays , nuclear test/fallout/waste/accidents

Question 22

How is ionizing radiation detected and measured?

Answer 22

Geiger müller tube -> most common instrument to detect and measure radiation
Radiation -> electrical impulses -> counting machine + clicks
Measures in count rates -> decays or counts/s

Other detectors:
Photographic film
Ionisation chambers
Scintillation counters
Spark counters

Question 23

How can you account of background radiation?

Answer 23

Measure radioactivity without the presence of a radioactive material

Do with radioactive material

Subtract -> correct count rate

Question 24

T or F: gamma radiation is the only type that changes the atom into a new element

Answer 24

False: alpha and beta change the atom into a different element, gamma doesn’t

Question 25

How does radioactive decay relate to reducing the nulceon number?

Answer 25

Alpha and beta:
Nucleus decays -> increase stability by reducing excess neutrons

Gamma:
Neutrons have too much energy -> radiation as gamma rays

Question 26

What is the word equation for alpha beta and gamma radiation?

Answer 26

Element X -> isotope of element Y + alpha particle

Alpha particle -> 2 proton, 2 neutron
Mass of element Y -> mass of element X - 4 (because lose 2 protons 2 neutron)
Atomic number of element Y -> atoms number of element X - 2 (lose 2 protons)

Element X -> isotope of element Y + beta particle
Beta -> neutron=proton + electron( beta particle)
Mass of element Y -> same (neutron replaced by proton)
Atomic number of element Y -> one more that element X (electron emitted/proton gained)

Element X -> element X + gamma rays
Everything stays the same except there gamma rays now

Question 27

Use nuclide notations in equations to show alpha, beta and gamma decay

Answer 27

Im not even going to just search it up

Question 28

What is a half life?

Answer 28

The time taken from half the nuclei of that isotope in any sample to decay

Question 29

How can you figure out the length of a half life from a graph?

Answer 29

Initial activity divided by 2 -> go across graph -> go down where it meets the curve

Question 30

What is the equation for activity over time (half life)?

Answer 30

Initial activity/2^x = activity over time

X=number of half lives

Question 31

Why will a graph for radiation decay never reach 0?

Answer 31

There will always be background radiation, and it must be taken into account for the graph to reach 0

Question 32

Why is ionizing radiation dangerous for humans?

Answer 32

It can cause damaged cell and tissue

Cell death
Tissue damage
Mutations
Cancer
Skin burns
Reduced amount of white blood cells

Question 33

How does ionizing radiation cause mutation?

Answer 33

If atoms that make up DNA are ionized -> strand is damaged

DNA becomes dead or mutated

Question 34

How are radioactive material handled, used and stored for safety?

Answer 34

Stored in lead lined boxes
When in used -> keep in a shielded container
Kept at a distance
Minimise amount of time handled
Never touch directly -> use tongs
Gloves and protective clothing

Disposing:
Buried underground in remote areas in lead lined containers

Safety for workers:
Workers that are exposed to radiation -> laws limiting amount they can get exposed to