Atoms and nuclear radiation

Question 1

What is an alpha particle?

Answer 1

a helium nucleus

2 protons, 2 neutrons

Question 2

What is a radioactive substance?

Answer 2

• atoms with unstable nuclei
• number of protons & neutrons is unbalanced

Question 3

What is radioactive decay?

Answer 3

• emission of radiation (random process)

Question 4

What is the activity of a substance?

unit

Answer 4

• the rate at which a radioactive substance decays
• measured in becquerels

Question 5

What can absorb alpha radiation?

Answer 5

• few cm of air
• piece of paper

Question 6

What are beta particles?

Answer 6

• electrons
• produced when a neutron spontaneously changes into a proton

Question 7

What can absorb beta radiation?

Answer 7

• thin sheet of aluminium

Question 8

What is gamma radiation?

Answer 8

• electromagnetic waves

Question 9

What can absorb gamma radiation?

Answer 9

• thick blocks of lead

Question 10

What is the symbol for gamma radiation?

Answer 10

Y

Question 11

What is the ionising power of each type of radiation?

Answer 11

• ionising power = ability to add or remove electrons in uncharged atoms to make them into charged particles
• alpha > beta> gamma

Question 12

What are the symbols for an alpha particle, beta particle, and neutron?

Answer 12

• 4/2 He
• 0/-1 e
• 1/0 n

Question 13

What is the half life of a radioisotope?

Answer 13

• the time taken for the number of radioactive nuclei in the substance to halve, or the time it takes for the activity of the substance to halve

Question 14

What is background radiation?

Answer 14

• a small amount of radiation around us
• due to the rocks in the earth, building materials, air, cosmic rays from the sun and space

Question 15

How are radioactive tracers used?

Answer 15

• path of the radioactive tracer is tracked through the body or system
• gives useful information about whether or not the body/ system is working correctly

Question 16

How does radiotherapy work?

Answer 16

• high doses of radiation kills cells
• traget directly at cancer cells
• cancer cells will be destroyed without damaging healthy cells nearby

Question 17

What is irridation?

Answer 17

• if an object is exposed to a radioactive source
• does not make object radioactive

Question 18

What is contamination?

Answer 18

• particles of a radioactive substance gets onto or into an object

Question 19

How do people protect themselves from radiation at their jobs?

Answer 19

• wear a lead apron
• stand behind a lead screen
• wear gloves
• use tongs

Question 20

Which type of radiation is the most dangerous in contamination?

Answer 20

• alpha
• all energy is absorbed in cell and cannot pass through

Question 21

Which type of radiation is the least dangerous in contamination?

Answer 21

• gamma
• little energy is absorbed by the cell
• easily passed out of the cell

Question 22

Which type of radiaton is the most dangerous in irridation?

Answer 22

• gamma
• can pass through the body

Question 23

What is nuclear fission?

Answer 23

splitting of heavy nuclei into lighter nuclei. this releases a huge amount of energy

Question 24

what does U-235 split into?

Answer 24

2 lighter nuclei and some neutrons

Question 25

Describe how bombarding U-235 with neutrons help with increasing the rate of fission

Answer 25

- becomes U-236 (very unstable) - splits into 2 lighter nuclei, 2-3 neutrons - gamma radiation produced

Question 26

What happens in a chain reaction?

Answer 26

- neutrons go on to make other nuclei unstable - controlled in a nuclear reactor to control the energy released - nuclear explosion is caused by uncontrolled chain reaction

Question 27

How is a fission reaction controlled?

Answer 27

- "**control rods**" (boron/ cadmium) **absorb neutrons** made from fission so that the chain reaction is reduced - can be moved further in/ out to **control rate** of reaction - all the way in = fission stops (all neutrons absorbed) - all the way out = fission occurs at highest rate -** graphite moderator** slows down neutrons - fission works more efficiently with slower speeds

Question 28

What is the main problem with nuclear fission?

Answer 28

- lighter nuclei produced is always **neutron rich- radioactive** - decays into more stable nuclei - **emits radiation** - reactor is surrounded with thick **concreate shield** to **absorb radiation**

Question 29

What is nuclear fusion?

Answer 29

- combining of light nuclei - the mass of the products of the reaction is always less than the mass of the nuclei that joined together, this "lost" mass is converted into energy