radioactivity

Question 1

who helped to develop the atomic model and their models? in order (5)

Answer 1

1. john dalton atoms are tiny spheres that can’t be broken up
2. jj thompson atoms are spheres of positive charge with tiny electrons stuck inside (plum pudding)
3. ernest rutherfood a positive nucleus surrounded by a cloud of electrons
4. niels bohr electrons orbit the nucleus at specific distances called energy levels
5. james chadwick the nucleus contains protons and neutrons

Question 2

describe the current atom model.

Answer 2

a tiny nucleus made of protons and neutrons. its radius is 10,000x smaller than the radius of the atom
most of the atom is empty space.
electrons occupy regions around the nucleus called electron shells.
the radius is around 1x10^-10. probably don’t need to know

Question 3

what happens if an electron gains or releases electro magnetic radiation?

Answer 3

it moves away from the nucleus. if it receives EM radiation
it moves closer to the nucleus. if it releases EM radiation

Question 4

what is an isotope?

Answer 4

an element with the regular amount of protons but a different amount of neutrons. giving them a different mass number

Question 5

what is radioactive decay?

Answer 5

when isotopes release radiation to become stable. they can also release neutrons

Question 6

what are alpha particles? α

Answer 6

2 neutrons and 2 protons released from the nucleus. the same as a helium nucleus

Question 7

what are the properties of an alpha particle? α

Answer 7

can only travel a few cm in air.
is absorbed by paper.
strongly ionising. because it has a large mass

Question 8

what are beta particles? β

Answer 8

a fast moving electron released by the nucleus when a neutron becomes a proton.

Question 9

what are the properties of a beta particle? β

Answer 9

can travel a few metres in air.
is absorbed by 5mm of aluminium.
moderately ionising. because it doesn’t weigh much
for every beta particle released a neutron in the nucleus turns into a proton.

Question 10

what is gamma radiation? γ

Answer 10

electro magnetic radiation released by the nucleus. with a short wavelength

Question 11

what are the properties of gamma radiation? γ

Answer 11

can travel long distances in air.
is absorbed by thick lead or concrete.
weakly ionising. because it has no mass

Question 12

what does it mean if radiation is strongly ionising?

Answer 12

the radiation interacts more frequently with what it is passing through meaning it quickly loses energy.

Question 13

what do nuclear equations show?

Answer 13

nuclear equations show radioactive decay using element symbols.
atom before decay → atom after decay + radiation emitted

Question 14

what happens to an atoms mass and charge atomic number when an alpha particle is released?

Answer 14

the mass decreases by 4.
the charge atomic number decreases by 2.

Question 15

what happens to an atoms mass and charge atomic number when a beta particle is released?

Answer 15

the mass stays the same
the charge atomic number increases by 1.

Question 16

what happens to an atoms charge and mass when gamma radiation is released?

Answer 16

nothing.
gamma radiation is just excess energy from the nucleus

Question 17

how can you measure how much radiation something is releasing?

Answer 17

use a geiger-muller tube part of a geiger counter which records the count rate. the number of radiation counts reaching the tube per second

Question 18

what is the half life of a source? of radiation

Answer 18

the time it takes for the amount of radiation released by a source to halve.

Question 19

what is activity and what is it measured in?

Answer 19

the rate that a source decays in becquerels
1 Bq = 1 decay per second

Question 20

what happens to the activity of a source every time it decays?

Answer 20

the activity decreases.

Question 21

what is background radiation?

Answer 21

the low level radiation that’s around all the time.

Question 22

what are the sources of background radiation? (3)

Answer 22

1. naturally occurring unstable isotopes. in air food building materials and rocks
2. cosmic rays from space.
3. radiation from human activity such as nuclear explosions or nuclear waste

Question 23

what is radiation dose measured in?

Answer 23

sieverts. 1 Sv = 1000 mSv

Question 24

what is irradiation?

Answer 24

simply being exposed to radiation. does not make something radioactive

Question 25

what is contamination?

Answer 25

when unwanted radioactive atoms get on or into something.

Question 26

what are the risks of radiation in cells?

Answer 26

1. tissue damage.
2. mutated cells which divide uncontrollably. cancer
3. kill cells completely causing radiation sickness

Question 27

what are 2 medical uses of radiation?

Answer 27

1.medical tracers. gamma
2. radiotherapy. gamma also

Question 28

what is nuclear fission?

Answer 28

splitting large unstable atoms into smaller atoms. the nucleus usually has to absorb a neutron to split unless spontaneous fission

Question 29

how can nuclear fission be used to generate electricity?

Answer 29

energy not transferred to the products of fission is carried away by gamma rays which can be used to heat water to turn turbines and generators.

Question 30

what are control rods used for? nuclear fission

Answer 30

control rods limit the energy produced by fission by absorbing released neutrons slowing down a chain reaction.

Question 31

what is nuclear fusion?

Answer 31

joining 2 nuclei to produce a larger nucleus.

Question 32

how can nuclear fusion be used to generate electricity?

Answer 32

energy is released when 2 nuclei join however we do not yet know how to use this energy.