unit 5

Question 1

the structure of an atom

Answer 1

a positively charged nucleus with negatively charged electrons around it

Question 2

how does the scattering of alpha particles by a sheet of thin metal of the atom prove the nuclear model of atom

Answer 2

the majority of them go straight through because the atom is mainly empty space

some are deflected through small angles because positive alpha particles are repelled by positive nucleus which contains most of the mass

a very small number of atoms are deflected straight back because the nucleus is extremely small

Question 3

how can positive ions be formed

Answer 3

when atoms lose electrons

Question 4

how can negative ions be formed

Answer 4

when atoms gain electrons

Question 5

what is an ion

Answer 5

an electrically charged atom formed by the loss or gain of electrons

Question 6

why do atoms gain or lose electrons

Answer 6

to become more stable

Question 7

how to know whether an atom is stable

Answer 7

there is the same number of protons and electrons

Question 8

how to know whether the ion is postive

Answer 8

more protons than electrons

Question 9

how to know whether the ion is negative

Answer 9

more electrons than protons

Question 10

what is the proton number

Answer 10

also know as atomic number
the number of protons in an atom

Question 11

what is the nucleon number

Answer 11

also known as the mass number
the total number of particles in the nucleus of the atom

Question 12

how can the number of neutrons be found

Answer 12

nucleon number - proton number -

Question 13

what is the charge of a proton

Answer 13

+1

Question 14

what is the charge of a neutron

Answer 14

0

Question 15

what is the charge of an electron

Answer 15

-1

Question 16

what are isotopoes

Answer 16

they are atoms of the same element that have an equal number of protons but a different number of neutrons
they tend to be more unstable due to the imbalance and are more likely to decay

Question 17

can elements have more than 1 isotope

Answer 17

yes

Question 18

what is nuclear fission

Answer 18

the splitting of a large, unstable nucleus into two smaller nuclei

Question 19

what happens during fission

Answer 19

the nucleus splits into two smaller nuclei as well as two or 3 neutrons
gamma rays are also emitted
the energy stored within the nucleus of atom

Question 20

what is the energy transfer in fission

Answer 20

energy transferred from nuclear potential to kinetic

Question 21

why does the mass change during fission

Answer 21

the mass of the products is less than the mass of the original nucleus
this is because the remaining mass has been converted into energy which is released during the fission process

Question 22

what is nuclear fusion

Answer 22

when two light nuclei join to form a heavier nucleus

Question 23

what is the problem with trying to replicate nuclear fusion

Answer 23

it requires extremely high temperatures to maintain

Question 24

where does the energy for nuclear fusion come from

Answer 24

the energy produced comes from a very small amount of the particles mass being converted into energy

Question 25

what is background radiation

Answer 25

the radiation that exists around us all the time

Question 26

what are the sources that contribute to background radiation

Answer 26

radon gas(in the air) rocks and buildings food and drink cosmic rays

Question 27

how can ionising nuclear radiation be measured

Answer 27

using a detector connected to a counter

Question 28

what is count rate

Answer 28

the count rate is the number of decays per second measured in count/s or count/min

Question 29

the happens when the source is further away from the detector

Answer 29

the count rate decreases because the radiation becomes more spread out the further away it is

Question 30

what is a corrected count rate

Answer 30

count rate - background radiation

Question 31

describe the emission of radiation from a nucleus

Answer 31

spontaneous and random in direction

Question 32

when do nuclei emit radiation

Answer 32

when they need to become more stable. it reduces the overall energy of the nucleus

Question 33

what is the process of emitting radiation known as

Answer 33

radioactive decay

Question 34

because radioactive decay is a random process, it means that:

Answer 34

equal probability of any nucleus decaying rate of decay is unaffected by surrounding conditions it is only possible to estimate the probability of a nuclei decaying in a given time period

Question 35

what are the different types of radioactive decay

Answer 35

alpha particles beta particles gamma radiation

Question 36

what does an alpha particle consist of

Answer 36

2 neutrons and 2 protons same as a helium nucleus

Question 37

what is the charge of an alpha particle

Answer 37

+2

Question 38

what are beta particles

Answer 38

they are fast moving electrons have a charge of -1

Question 39

what are gamma rays

Answer 39

they are electromagnetic waves and have the highest energy they have no charge

Question 40

what is the penetrating power of alpha particles

Answer 40

stopped by paper

Question 41

what is the penetrating power of beta particles

Answer 41

stopped by a few mm of aluminum passes through paper

Question 42

what is the penetrating power of gamma rays

Answer 42

very high, can only be stopped by lead

Question 43

what is ionisation

Answer 43

the process of which an atom becomes negative or positive by gaining or losing electrons all nuclear radiation is capable of ionising atoms

Question 44

what happens when an atom is ionised

Answer 44

the number of electrons is has changes

Question 45

how ionising are alpha particles

Answer 45

they are the most ionising form of radiation because they leave a dense trail of ions behind them, affecting all atoms

Question 46

how ionising are beta particles

Answer 46

they are moderately ionising leave a less dense trail then alpha but are usually more dangerous

Question 47

how ionising are gamma rays

Answer 47

least ionising form of radiation but still can be dangerous

Question 48

what factors does the ionising effect depend on

Answer 48

the greater the charge of the radiation, the more ionising it is the higher the kinetic energy of the radiation, the more ionising it is (alpha is highest because highest mass)

Question 49

what are the ranges of the types of radiation from shortest to longest

Answer 49

alpha (shortest) beta gamma rays (infinite)

Question 50

when are particles deflected in an electrical field

Answer 50

if it has charge

Question 51

when are particles deflected in a magnetic field

Answer 51

if it has charge and is moving perpendicular to it

Question 52

what particles are deflected by electric and magnetic fields

Answer 52

alpha and beta gamma has no charge so no deflection

Question 53

in an electric field, which way are alpha particles deflected towards

Answer 53

towards the negative plate

Question 54

in an electric field, which way are beta particles deflected towards

Answer 54

the positive plate

Question 55

how does gamma radiation move in an electric field

Answer 55

not deflected so passes straight through between the plates

Question 56

what happens during alpha or beta particle decay

Answer 56

the nucleus changes to that of a different element

Question 57

why may isotopes be radioactive

Answer 57

because there is an excess of neutrons or the nucleus is too heavy

Question 58

what is half life

Answer 58

the time taken for half the nuclei of that isotope in any sample to decay

Question 59

how is radiation useful in smoke detectors

Answer 59

the alpha radiation will ionise the air within the detector, creating a current when theres smoke, the alpha emitter is blocked the alarm is triggered due to no current

Question 60

how can radiation be used to measure the thickness of materials

Answer 60

beta particles are used and depending on the thickness, the amount of particles being absorbed will be more or less. this can be used to regulate the thickness of materials

Question 61

how are gamma rays used in the diagnosis and treatment of cancer

Answer 61

gamma rays penetrate the body and kill the bacteria or cancer cells

Question 62

how can radiation be used to sterilise food and medical equipment

Answer 62

gamma rays are used because objects can be sterilized without the packaging being removed it kills any microorganisms

Question 63

what are the effects of ionising nuclear radiations on living things

Answer 63

cell death mutations cancer

Question 64

how are radioactive sources stored safely

Answer 64

storing them in lead lined boxes and keeping distance minimising the amount of time the source is handled

Question 65

how is radioactive waste disposed of

Answer 65

by burying them underground to prevent it from being released into the environment