P7 - Radioactivity

Question 1

What is the nucleon number?

Answer 1

Number of protons plus neutrons

Question 2

What is the relative masses of a proton, neutron and electron?

Answer 2

Electron - 0.0005
Proton - 1
Neutron - 1

Question 3

Is the proton number on the bottom or top on the periodic table symbol?

Answer 3

It is on the bottom and is always the smaller number

Question 4

What is ionising radiation?

Answer 4

The radiation emitted from unstable nuclei, that when in contact with a neutral atom can dislodge an electron and make it an ion. Made up of alpha, beta and gamma radiation.

Question 5

Describe dalton’s model of the atom.

Answer 5

-All matter is made up of small, indivisible spheres.
-atoms of the same element are the same size and weight.
-During chemical reactions atoms rearrange to form different substances.

Question 6

Describe the plum pudding model.

Answer 6

Atoms are positively charged spheres, with negatively charged electrons embedded within, like plums in a pie.

Question 7

Describe the gold foil experiment?

Answer 7

It involved bombarding a thin sheet of gold foil with alpha particles, surrounded by a material that flashed when in contact with the alpha material.

Question 8

Who created the gold foil experiment?

Answer 8

Ernest Rutherford

Question 9

What were the takeaways from the gold foil experiment?

Answer 9

-showed nucleus was very, very small
-showed atom was mostly empty space
-most of atoms mass in nucleus
-nucleus was positively charged

Question 10

What does ionising mean?

Answer 10

How well it rips off electrons .

Question 11

What is the unit for radioactivity?

Answer 11

Becquerells (Bq)

Question 12

What is an alpha particle?

Answer 12

A helium nucleus

Question 13

What is a beta particle?

Answer 13

A fast moving electron

Question 14

What is a gamma particle?

Answer 14

A wave

Question 15

What stops the different radioactive particles?

Answer 15

Alpha - skin/paper
Beta - thin aluminium
Gamma - thick lead

Question 16

What is the difference between ionising power and penetrating power?

Answer 16

Ionising power is how ionising (dangerous) the particle is and penetrating power is how easily it passes through objects.

Question 17

how do you do an alpha decay equation?

Answer 17

unstable atom -> more stable atom ( minus ^4 and 2) + helium nucleus (^4 and 2)

Question 18

Practise a beta decay question

Question 19

Practise a gamma decay question

Question 20

What is background radiation?

Answer 20

Naturally things around us and people release some radiation. This is called background radiation.

Question 21

How do you work out the uncertain of the mean background count?

Answer 21

Uncertainty = range of readings / 2

Question 22

What equipment do you use to measure radioactive activity?

Answer 22

A Geiger counter

Question 23

What is half-life?

Answer 23

Either…
- the time taken for the count rate to halve
- or the time taken for half of the radioactive nuclei in a sample to decay.

Question 24

How can you calculate half-life?

Answer 24

Amount after N half lives = (1/2)^N x initial amount

Question 25

What is a radioactive tracer ?

Answer 25

A tracer contains a radioactive isotope that emits gamma radiation that can be detected from outside the body. We can use this to check that parts of the body are functioning correctly e.g. if a kidney is blocked.

Question 26

Why might you use radioactive iodine as a medical tracer?

Answer 26

• as it has a half life of 8 hours so will be long enough to carry out experiment but also not too long that the patient will be at risk of ionisation.
• emits gamma radiation which is easily detected outside the body
• the daughter nuclei are stable so the radiation will stop once out of system.

Question 27

How does radiotherapy work?

Answer 27

It works by firing a narrow beam of highly ionising radiation at cancerous cells, to kill them off. To stop all surrounding cells being killed the beam is rotated to make sure the cancerous cells are killed but surrounding cells aren’t exposed long enough to be killed.

Question 28

What is nuclear fission?

Answer 28

A type of nuclear reaction that is used to release energy from large unstable atoms by splitting them into smaller atoms. This rarely happens spontaneously, usually the nucleus will absorb a neutron before it will split.

Question 29

Describe the process of nuclear fission?

Answer 29

1) a slow neutron is absorbed by a uranium-235 nucleus
2) the resulting nucleus of uranium-236 is unstable
3) the nucleus splits apart into 2 lighter nuclei( daughter nuclei), 3 neutrons and gamma radiation.
4) the process then happens again as the 3 neutrons then get absorbed by another uranium-235 nucleus.

Question 30

What type of reaction is nuclear fission?

Answer 30

A chain reaction

Question 31

Name the different pieces of equipment used to control the nuclear fission and what they do.

Answer 31

• graphite moderator, slows down the released neutrons so they can be absorbed by the next atom
• boron control rods, are raised or lowered to change speed of reaction. When these are lowered fully the reaction is stopped.
• concrete shielding - prevents radiation escaping from the core.
• hollow fuel rods, contain pellets of uranium fuel.

Question 32

Give 2 pros and 2 cons of nuclear power.

Answer 32

Pros
1) low greenhouse gas emissions
2) high energy density
Cons
1)radioactive waste
2)potential for accidents

Question 33

What is nuclear fusion ?

Answer 33

Nuclear fusion is a process in which two lighter nuclei combine to form a heavier nucleus, releasing a large amount of energy in the process.

Question 34

What are the major drawbacks of nuclear fusion?

Answer 34

-To start the reaction off the nuclear fuel must be heated up to around 150 million degrees
-keeping plasma contained is very hard.
-easily disrupted.