Radioactivity

Question 1

What does a nucleus atom contain?

Answer 1

• Protons and Neutrons
• makes up Mass of the atom
• doesn’t take up space because it’s TINY

Question 2

Atomic number / proton number

Answer 2

number of protons in nucleus

Question 3

Mass number

Answer 3

Total number of protons and neutrons in a nucleus

Question 4

Electrons

Answer 4

-negative charge
-really small
-whizz around outside of atom
-paths take up a lot of space

Question 5

Atoms are neutral so…

Answer 5

No. Protons = No. Electrons

Question 6

Define Isotopes

Answer 6

Atoms with the same number of protons but different number of neutrons (diff mass no.)

Question 7

Each element only has..

Answer 7

1-2 stable isotopes

Question 8

Radioactive isotopes

Answer 8

-nucleus is unstable➡️decays and emits radiation

Question 9

Unstable nuclei:

Answer 9

break down at Random

Question 10

Nucleus decay

Answer 10

-Spontaneously in its own time
-unaffected by temperature/chemical bonding
-when nucleus does decay it splits out 1or more types of radiation (alpha, beta, gamma, neutrons)
-nucleus often changes to new element

Question 11

Nuclear radiation causes ionisation by…

Answer 11

-Bashing into atoms and knocking electrons off of them
-atoms to ions➡️ionisation

Question 12

Ionisation pattern

Answer 12

Further the radiation can penetrate before hitting an atom and getting stopped, the less damage it will do along the way = less ionising it is

Question 13

What can be used to to detect ionising radiation

Answer 13

-Geiger-Müller detector
-photographic film

Question 14

Alpha particles

Answer 14

-2 protons 2 neutrons
-big heavy, slow moving
-don’t penetrate far into materials
- stopped quickly

Question 15

Why do alpha particles create lots of ions

Answer 15

Because of big size - strongly ionising - bash into a lot of atoms & knock electrons off

Question 16

Are alpha particles positively charged or negatively

Answer 16

-Positively - deflected by electric/magnetic fields
-emitting alpha particle decreases atomic number of nucleus by 2 and mass number by 4

Question 17

Define Beta particles

Answer 17

electron emitted from nucleus of atom when neutron turns into proton/electron

Question 18

What happens when a beta particle is emitted

Answer 18

Number of protons in nucleus increases by 1 - atomic number increases by 1, mass number stays same

Question 19

Beta particles moving

Answer 19

-FAST and small

Question 20

Beta particles penetrating

Answer 20

Penetrate moderately before ionising

Question 21

Are beta particles charged positively or negatively?

Answer 21

Negatively- deflected by electric and magnetic fields

Question 22

Gamma rays

Answer 22

-short wave lengths
- no mass just energy
-penetrate long way into materials without being stopped
-weak ionising - pass through rather than collide

Question 23

Do Gamma rays have charge

Answer 23

No charge, not deflected by magnetic /electric fields

Question 24

Gamma rays emissions

Answer 24

-Always happens after beta alpha decay
-no effect on atomic /mass number of isotope

Question 25

What are alpha particles blocked by

Answer 25

Paper, skin, few cm of air

Question 26

What are beta particles blocked by

Answer 26

Thin metal

Question 27

What are gamma rays blocked by

Answer 27

Thick lead, very thick concrete

Question 28

Do radioactive samples always decrease over time

Answer 28

Yes

Question 29

Do older samples have more or less radiation

Answer 29

Less because the activity of an unstable nuclei decreases

Question 30

Define half life

Answer 30

Time taken for activity to fall by half * short half life activity falls quickly * long half life falls more slowly

Question 31

Beta and gamma will penetrate the skin and other body tissues this makes them suitable for…

Answer 31

Medical tracers

Question 32

What can radiation treat

Answer 32

Cancer: ionising radiation can kill/damage cells, but once cancer started then ionising radiation an be used to react as well

Question 33

RADIOTHERAPY

Answer 33

-Kills cancer cells stops dividing -high doses of gamma rays

Question 34

Gamma rays and sterilising equipment

Answer 34

Irradiation: Food and medical equipment can be irradiated with high doses of gamma rays to kill microbes without damaging food/ equipment (not high temperatures)

Question 35

Radiation used in industry for tracers and thickness gauges

Answer 35

Detects leaks in under pipes

Question 36

What is beta radiation used for

Answer 36

Thickness control

Question 37

Ionising radiation damaging cells and tissues

Answer 37

Beta and gamma penetrate the skin AND soft tissues to reach delicate organs -more HAZARDOUS

Question 38

Risks for alpha radiation

Answer 38

-Cannot penetrate skin -do all their damage in very localised area

Question 39

How does radiation damage cells

Answer 39

Collides with molecules- more exposure more damage

Question 40

What do lower doses of radiation cause to us

Answer 40

Minor damage - can cause mutations - cells divide uncontrollably - cancer

Question 41

Objects near a radioactive source are ———— by it

Answer 41

Irradiated

Question 42

Ways to reduce risk of irradiation

Answer 42

-keep sources in lead lined boxes -standing behind barriers -being in different room - remote controlled arms

Question 43

What is contamination

Answer 43

Radioactive particles getting onto objects

Question 44

What happens when atoms are contaminated

Answer 44

- decay releases radiation which may cause harm - very dangerous if enters body

Question 45

How to prevent contamination

Answer 45

Use gloves, tongs, protective suits, masks

Question 46

Is radioactive waste easily disposed safely

Answer 46

No

Question 47

Where is low level radioactive waste from nuclear power stations and hospitals disposed

Answer 47

Clothing, syringes buried in secure landfill sites

Question 48

How do we dispose of high level radioactive waste

Answer 48

-It is really dangerous- since it stays highly radioactive for tens of thousands of years -sealed into glass blocks then sealed in metal canisters then buried deep under ground - geologically stable place

Question 49

What do nuclear power stations use

Answer 49

Nuclear FISSION chain reaction

Question 50

Define Nuclear Fission

Answer 50

Splitting of atoms that release energy -eg. Uranium-235

Question 51

Neutrons released by fission reactions in a nuclear reactor have a lot of energy. How are these absorbed by uranium nuclei and sustain the chain reaction?

Answer 51

Need to be slowed down by a moderator: Graphite, Water which slows down neutrons

Question 52

What limits the rate of fission

Answer 52

Control rods made of boron by absorbing excess neutrons

Question 53

High energy neutrons and gamma rays are released in fission are highly penetrating ionising radiation what absorbs the ionising radiation?

Answer 53

Shielding: thick concrete structure containing lead or other metals

Question 54

What is nuclear FUSION

Answer 54

OPPosite of nuclear FISSION: 2 nuclei collide at HIGH speed and FUSE to create a larger heavier nucleus.

Question 55

Does the heavier nucleus have more mass

Answer 55

Not as much as the 2 separate nuclei did. some lighter nuclei are converted into energy and released

Question 56

Does FUSION release a lot of energy?

Answer 56

Yes, all the energy released in stars come form fusion

Question 57

What is the big problem with fusion only happening in…

Answer 57

Really high temperatures since positively charged nuclei have to get really close to fuse so they move really FAST to overcome force from ELECTROSTATIC REPULSION