Radioactivity

Question 1

the structure of an atom

Answer 1

-positively charged nucleus, consisting of protons and neutrons,
- surrounded by negatively charged electrons,
- all of the mass in the nucleus
- mostly consisting of empty space

Question 2

what is the size of an atom

Answer 2

__ x 10 ^-10

Question 3

what is an isotope

Answer 3

same number of protons and electrons, but different number of neutrons
eg carbon-12 carbon-13

Question 4

how is the charge of an atom decided

Answer 4

no charge - equal number proton and electrons
negative charge - more electrons
positive charge - less electrons than protons

Question 5

when do electrons change orbits

Answer 5

when there is absorption of electromagnetic radiation electrons can move usually away from the nucleus

Question 6

what happens when electron move orbits ( shells)

Answer 6

When the atom has absorbed EM radiation electrons move to a higher orbit (further from the nucleus)

-When the atoms has gives out (emitted) EM radiation the electrons falls to a lower orbit (closer to the nucleus)

Question 7

explain ionisation

Answer 7

-when electrons gaining so much energy it can leave the atom
- atom forms an ion

Question 8

how do nucleus give out radiation

Answer 8

• the nucleus of a radioactive substance become unstable
• so the nucleus can easily change or decay
• when it decay radiation is emitted from the nucleus in order to make it loose energy to become stable
  -it is a random process

Question 9

what are the types of radiation which can be emitted during nucleus decay

Answer 9

alpha α
beta plus (positrons) β+
beta minus β-
gamma rays γ

Question 10

ionisation and penetrating levels of radiation

Answer 10

Alpha particles - very ionising and not penetrating

beta particles - moderately ionising and moderately penetrating

gamma radiation - weak ionising and very high penetration

Question 11

what different types of radiations are stopped

Answer 11

Alpha particles
stopped by paper

beta particles
stopped by 3mm lead

gamma radiation
stopped by thick lead or concrete

Question 12

what is back ground radiation

Answer 12

Radiation that is found in small quantities all around us and originates from natural sources such as rocks and cosmic rays as well as from man-made sources such as nuclear weapons testing and accidents

Question 13

sources of natural sourced back ground radiation

Answer 13

radioactive gas ( mainly radon) can be produced out of rocks contain some uranium and can be built up under housing when there is poor ventilation

Question 14

what is the sources of background radiation from solar system

Answer 14

cosmic rays - high energy, charged particle stream out of the sun and stars and are a form of radiation

Question 15

how can you measure radiation

Answer 15

using a Geiger-muller tube - where radiation passes through the tube and creates a short pulse of current.

photographic film - the darker film gets the more radiation absorbed by the film, more radiation present
badges worn by people who work with radiation to see how much radiation they have come in contact with

Question 16

what is the decay process that turn nucleus into alpha particles

Answer 16

when a nucleus get rid of electrons and other protons and neutrons to have:
2 protons
2 neutrons
0 electron
+2 charge
same as a helium atom and can be written as α or H 4(top) 2 (bottom)

• same as a helium nucleus

Question 17

what are beta plus (positron) particles / decay process

Answer 17

beta + / positrons - high energy, high speed particles with the same mass of an electron but a charge of plus one

• same as an electron emitted from a nucleus

the decay of a proton turns into a neutron and emits a positron (beta +) with a positive charge

Question 18

what are beta minus / decay process

Answer 18

beta - are high speed high energy electrons with a negligible mass and charge of -1

• same as an electron emitted from a nucleus

the decay of a neutron which makes an electron which is emitted and a proton

Question 19

what are gamma rays / decay process

Answer 19

high frequency electromagnetic waves which do not have an electric charge.
it is emitted as a result of nuclei after a decay having excess energy which they release as gamma radiation

Question 20

what is activity?

Answer 20

the number of decays in a sample per second
measures in becquerel, Bq

Question 21

why does activity decrease over time?

Answer 21

over time the nucleus will radiate to loose energy to become more stable, due to decay the nuclei will become more stable
so activity decreases over time

Question 22

what is meant by half - life?

Answer 22

the time taken for half the unstable nuclei in a sample of a radioactive isotope to decay

Question 23

dangers of ionising radiation -
a short half - life

Answer 23

initially very dangers and radioactive
but dies down quickly
so a short term risk

Question 24

dangers of ionising radiation - long half - life

Answer 24

the source will remain weakly radioactive for a very long time

Question 25

safety measures when using radioactivity

Answer 25

limiting patient doses
- radioactivity has a short half-life so can be removed quickly

limiting risks to medical personnel
- they leave the room during radioactivity test as close proximity every day to radioactive sources puts health at risk

Question 26

what is the difference between contamination and irradiation

Answer 26

contamination
-lasts for a long time
-the source of radiation is transferred to an object to now the object gives of radiation

irradiation
-last for a short time
- the source emits radiation on to an object which is now contaminated with radiation

Question 27

uses of radioactivity ( gamma)

Answer 27

Irradiating foods
gamma rays enter food and kill microorganisms found on it

sterilisation of equipment
gamma rays kills all the microbacteria present on equipment so they are safe for surgeries

used to treat cancer
by shooting beams of gamma rays to kill cancer cells

Question 28

uses of radioactivity ( alpha)

Answer 28

used in smoke alarms
alpha particles, ionise in the air and makes a current
if smoke enter the air around the alarm the current drops in the circuit which sounds the alarm

Question 29

uses of radioactivity (beta)

Answer 29

to check the thickness of paper and to see if there are any defects ion the production of paper

Question 30

what is nuclear fission

Answer 30

where large nuclei break up to form small nuclei and release energy

Question 31

explain the chain reaction which occurs with nuclear fission

Answer 31

1) a neutron is absorbed by uranium - 235 nuclei
2) the uranium -236 nuclei is now unstable and splits and releases more nuclei
3)this causes an uncontrollable chain reaction where all the neutrons join more uranium 235 which continues the process to make energy

Question 32

what is the purpose of control rods during a nuclear fission

Answer 32

control rods are placed in the centre of the reactor core which absorbs the neutrons so the chain reaction slows down .
if the rate of fission needs to be increase the control rods are taken out

Question 33

what is the purpose of fuel rods

Answer 33

they release neutrons which fly out and cause nuclear fission

Question 34

what is the purpose of the coolant

Answer 34

• the hot coolant is pumped into a heat exchanger, which makes steam.
• the steam drives a turbine which produces electricity

Question 35

what is nuclear fusion

Answer 35

two small nuclei joining together to form a larger nuclei.
fusion reactions release energy inside the sun

Question 36

where does nuclear fission occur

Answer 36

in the sun where helium is joined together due to high pressure and temperature

Question 37

how does nuclear fusion work

Answer 37

1) very high pressures in the sun and very hot temperature.
2) the helium nucleus have electrostatic repulsion to each other
3)the high temp and pressure over come the repulsion if the nuclei move faster and collide more
4) this causes a great mount of energy to be made