2.5 Radioactivity

Question 1

Isotopes

Answer 1

Different forms of the same element - other isotopes tend to be unstable and radioactive meaning they give out nuclear radiation and decay into other elements

Question 2

Alpha

Answer 2

• two neutrons and protons have a nucleon number of 4 and a charge of 2
• relatively big, heavy and slow moving

Question 3

Nucleon Number

Answer 3

How many protons and neutrons in an atom

Question 4

Beta

Answer 4

• high energy electron, virtually no mass
• charge of -1
• move fast and are small
• emit when neutron turns into a proton

Question 5

Gamma

Answer 5

• spitting out alpha or beta particles
• nucleus needs to get rid of extra energy - electromagnetic wave
• no mass and no charge they are just energy so they don’t change element

Question 6

Radiation Penetrates Materials

Answer 6

• alpha don’t get very far before hitting atoms (blocked by paper)
• beta can travel very far before hitting atoms (blocked by thin aluminium)
• gamma radiation travel a long way before hitting atoms (blocked by thick lead)

Question 7

Alpha Radiation Equations

Answer 7

• nucleon number decreases by 4 loosing 2 neutrons & 2 protons
• a new element will be formed
• Ra ——> Rn + Alpha
• 226 ——> 222 + 4 (nucleon)
• 88 ——> 86 + 2 (proton)

Question 8

Beta Radiation Equations

Answer 8

• nucleus emits a beta particle and neutron changes into proton
• nucleon does not change - lost a neutron but gained a proton
• C ——> N + Beta
• 14 ——> 14 + 0 (nucleon)
• 6 ——> 7 + (-1) (proton)

Question 9

Gamma Radiation Equations

Answer 9

• nucleon number and proton number don’t change
• Pa ——> Pa + Gamma
• 234 ——> 234 + 0 (nucleon)
• 91 ——> 91 + 0 (proton)

Question 10

Radioactivity

Answer 10

Random process when radiation is given out by a sample and can be measured with a geiger-muller tube and counter rate

Question 11

Radioactive Decay

Answer 11

Random with a constant probability that an unstable nucleus will decay

Question 12

Constant Probability Practical

Answer 12

1) get a sample of dice - at least 50
2) roll and count how many land on 6 because they represent decayed nuclei
3) remove decayed ones and roll
4) repeat till all dice roll a 6
5) 1 unit of time passing is how many roles
6) plot a graph
7) use decay cure to calculate half-life
8) repeat

Question 13

Background Radiation

Answer 13

• low level radiation that is present all the time
• naturally occurring unstable isotopes are in air, food, building materials and rocks, cosmic rays
• plants absorb radioactive isotopes
• x-rays in hospitals produces artificial background radiation

Question 14

Accidents at Power Plants

Answer 14

Lead to high levels of background radiation in the environment

Question 15

Dosage/Damage of BR

Answer 15

• everyone revives a small dose of radiation form BR
• dose determines how much damage it causes
• high dose = more chance of cancer

Question 16

Radon

Answer 16

• produced by certain underground rocks - granite
• tends to get trapped inside peoples houses but you can install census and flooring to stop this

Question 17

BR in experiments

Answer 17

You have to account for it otherwise it will record results higher than they should be - average count rate over a long enough time then subtract from count rate of a radioactive source

Question 18

Dangers of Nuclear Radiation

Answer 18

• it can enter living cells and interact with molecules
• ionisation (charged particles)
• lower dose = damaging mutations
• higher dose = kill cells completely

Question 19

Radiation that’s dangerous outside the body

Answer 19

gamma and beta
they can pass through the skin and get inside organs

Question 20

Radiation that’s dangerous inside the body

Answer 20

alpha because it’s the most ionising and does damage in localised areas

Question 21

Waste Products of Radioactive Process

Answer 21

Low level from nuclear power stations and hospitals, high levels of waste have long half life and can stay radioactive for a long time, when disposing of it in cool pools for 7 years and then sealing them in metal containers and inject waste in rocks

Question 22

Medicine

Answer 22

Certain radioactive isotopes emit gamma radiation used as tracers in the body because it can pass out, to see if organs work correctly, relatively short half life so it’s safe to go in your body

Question 23

Cancer Treatments

Answer 23

High doses of radiation will kill living cells, radiation is directed carefully so it kill cancer cells without damaging too much, radiation is used to remove tumours completely or control spreading

Question 24

Treating Cancer Externally

Answer 24

Gamma rays focused on tumour using a wide beam, beam is rotated round with tumour at centre, minimising exposure - treatment given in doses with time between healthy cells to repair or replace

Question 25

Treating Caner Internally

Answer 25

Using implants to attack the tumour containing beta emitters and are placed next to or inside the tumour, short half life can be left in but long half life must be taken out so it doesn’t damage other tissue
Alpha can be injected it’s ionising

Question 26

Carbon Dating

Answer 26

• property of being able to form molecular bonds with up to four other atoms
• carbon is consistently decaying because it is radioactive