t4- atomic structure

Question 1

why do unstable nuclei give out radiation

Answer 1

they undergo decay to become more stable
as they release radiation, their stability increases

Question 2

what is the process called when unstable nuclei give out radiation to become stable

Answer 2

radioactive decay

Question 3

what is the activity of an unstable nucleus

Answer 3

rate at which a source of unstable nuclei decays

Question 4

what is the unit for radioactive activity

Answer 4

becquerel (Bq)

Question 5

what is count-rate

Answer 5

number of radioactive decays per second

Question 6

give an example of something that can measure count-rate

Answer 6

geiger-muller tube

Question 7

state 4 types of nuclear radiation

Answer 7

alpha particles
beta particles
gamma ray
neutrons

Question 8

what are the constituents of an alpha particle

Answer 8

2 protons and 2 neutrons
same as a helium nucleus

Question 9

what is the range of an alpha particle through the air

Answer 9

a few cm

Question 10

what stops beta radiation from passing through a point

Answer 10

thin sheet of aluminium
a few m of air

Question 11

what stops gamma rays from passing through a point

Answer 11

few cm of lead
few m of concrete

Question 12

which type of radiation is most ionising

Answer 12

alpha

Question 13

which type of radiation is least ionising

Answer 13

gamma

Question 14

describe the nature of radioactive decay

Answer 14

random
it is impossible to predict which nuclei will decay and when

Question 15

what is the half-life of a radioactive isotope

Answer 15

the time it takes for the number of the unstable nuclei to halve

Question 16

what is radioactive contamination

Answer 16

the presence of unwanted radioactive nuclei on other materials

Question 17

what is irradiation

Answer 17

the process of exposing a material to nuclear radiation
the material does not become radioactive

Question 18

why is it important for the results of studies on the effect of radiation to be shared with other scientists

Answer 18

peer review- to allow findings to be independently checked

Question 19

give 4 sources of background radiation

Answer 19

rocks
cosmic rays from space
nuclear weapon testing
nuclear accidents

Question 20

what is the unit for radiation dosage

Answer 20

sieverts (Sv)

Question 21

how might radiation dosage that different people experience differ

Answer 21

some work involves working with radiation
background radiation differs with location eg. locality of nuclear power stations

Question 22

what determines how dangerous a radioactive isotope is

Answer 22

its half life

Question 23

why are isotopes with long half-lives harmful

Answer 23

they remain radioactive for longer periods of time
they must be stored in particular ways to avoid humans/environment from being exposed to radiation for too long

Question 24

what are 2 uses of nuclear radiation in medicine

Answer 24

examining internal organs
controlling and destroying unwanted tissue

Question 25

how is radiation used in sterilisation

Answer 25

gamma emitters kill bacteria on the equipment

Question 26

explain the process of radiotherapy

Answer 26

gamma emitters direct gamma rays at cancerous cells
cancerous cells absorb the radiation and are killed

Question 27

how are medical tracers chosen

Answer 27

they should have a short half-life and should decay into a stable isotope which can be excreted
should only release gamma radiation since it is weakly ionising and can easily pass through body tissue without damaging it

Question 28

what is nuclear fission

Answer 28

the splitting of a large, unstable nuclei into smaller, more stable nuclei

Question 29

give an example of a fissionable isotope

Answer 29

uranium-235

Question 30

what usually needs to happen to induce fission

Answer 30

the unstable nuclei must absorb a neutron

Question 31

what is emitted in a fission reaction

Answer 31

2 smaller nuclei
2/3 neutrons
gamma rays
energy

Question 32

what takes place during a chain reaction in a nuclear reactor

Answer 32

unstable nucleus absorbs neutron
nucleus undergoes fission and releases 2/3 further neutrons
these induce more fission , resulting in a chain reaction

Question 33

what is the consequence of an uncontrolled chain reaction

Answer 33

the rate of fission events becomes too high and results in the production of too much energy
can lead to a nuclear explosion

Question 34

what is nuclear fusion

Answer 34

the joining of 2 light nuclei to produce heavier nuclei and release energy

Question 35

why is it more difficult to generate energy through nuclear fusion

Answer 35

requires high temperatures which requires large amounts of energy

Question 36

why isn’t nuclear fusion currently a viable way to produce energy on earth

Answer 36

energy required would be greater than energy produced, resulting in a net energy loss

Question 37

what is a beta particle

Answer 37

– a high speed electron ejected from the
nucleus as a neutron turns into a proton