7 Radioactivity and Particles

Question 1

Describe the structure of an atom in terms of protons, neutrons and electrons

Answer 1

tiny, dense nucleus (made up of protons and neutrons) at their centre, with electrons orbiting around the nucleus in shells

Question 2

Define atomic(proton) number

Answer 2

number of protons in an atom - always the same

Question 3

Define mass(nucleon) number

Answer 3

number of protons and neutrons in nucleus

Question 4

Define isotope

Answer 4

Atoms with the same number of protons but different numbers of neutrons

Question 5

How are alpha (α) particles, beta (β−) particles, and gamma (γ) rays emitted ?

Answer 5

ionising radiations emitted from unstable nuclei in a random process

Question 6

RADIOACTIVITY AND PARTICLES

Question 7

units for:

frequency of decay :
distance :

time :

Answer 7

frequency of decay : becquerel (Bq), 1 (Bq) for 1 decay / sec

distance : centimetres (cm), normally however is (m)

time : hour (h), minute (min) but normally (s)

Question 8

describe structure of an atom

Answer 8

Atoms are made up of protons, neutrons and electrons.

Protons and neutrons are in the nucleus, electrons are in the shells

Question 9

define:
atomic number
mass number
isotope

Answer 9

Atomic (proton) number is the number of protons in the nucleus of an atom.

Mass (nucleon) number is the total number of protons and neutrons in the nucleus of an atom.

An isotope is an atom of the same element, same number of protons, different number of neutrons

Question 10

alpha (α) particles, beta (β−) particles, and gamma (γ) rays are ionising radiations emitted from ______ nuclei in a ______ process

Answer 10

unstable
random

Question 11

can one radioactive source release different types of radiation?

Answer 11

yes

Question 12

what is ionisation

Answer 12

when an atom loses or gains an electron, causing it to become an ion (an atom which is positively or negatively charged).

Question 13

describe nature of alpha (α) particles
ionising
penetration
stopped by:
nature of radiation:

Answer 13

strong ionising
weak penetration
stopped by paper
nature of radiation: helium nucleus
4
He
2

Question 14

describe nature of alpha (α) particles
ionising
penetration
stopped by:
nature of radiation:

Answer 14

moderate ionising
moderate penetration
stopped by: 5mm aluminium
nature of radiation: fast moving electron
0
e
-1

Question 15

describe nature of gamma (γ) rays
ionising
penetration
stopped by:
nature of radiation:

Answer 15

weak ionising
strong penetration
stopped by: 10cm lead
nature of radiation: em wave
0
γ
0

Question 16

practical: investigate the penetration powers of different types of radiation using either radioactive sources or simulations

Answer 16

Detect using a Geiger Müller Tube.

Try the three different materials in order, paper then aluminium then lead.

Count rate will significantly decrease if radiation is stopped.

Question 17

describe alpha decay in terms of atomic and mass numbers

Answer 17

2 protons and 2 neutrons are lost.

· Mass number decreases by 4

· Atomic number decreases by 2

Question 18

describe beta decay in terms of atomic and mass numbers

Answer 18

· 1 neutron is converted to an electron (lost from the atom) and proton

· Mass number is unchanged

· Atomic number increases by 1

Question 19

describe gamma decay in terms of atomic and mass numbers

Answer 19

· Energy is lost from an atom in the form of an electromagnetic wave

· Mass number is unchanged

· Atomic number is unchanged

Question 20

describe neutron radiation in terms of atomic and mass numbers

Answer 20

In neutron-rich nuclides, occasionally one or more neutrons are ejected. They are also emitted during nuclear fission.

The nucleus becomes a new isotope of the original element

Question 21

Photographic film:

Radiation will cause photographic film to ______ . They are worn as badges by people who work with radiation, to check how much exposure they have had

Answer 21

darken

Question 22

sources of background (ionising) radiation from Earth and space

Answer 22

radon in air
Granite in rocks
Cosmic rays
Medical equipment - x rays from mri scanners
Food and drink containing radioactive isotopes

Question 23

Geiger Müller detector:

When connected to a counter, the detector will be able to measure _________ . Each time it absorbs radiation, it transmits an electrical pulse to the machine, which
produces a clicking sound. The greater the frequency of clicks, the more radiation present.

Answer 23

radioactivity

Question 24

activity of a radioactive source ______ over a period of time and is measured in ___________

Answer 24

decreases
becquerels

Question 25

define half life

Answer 25

time taken for the radioactivity of a specific isotope to fall to half its original value.

Question 26

uses of radioactivity in industry smoke detectors thickness monitoring for metal sheets

Answer 26

o Smoke detectors Long half-life alpha emitters are used in smoke detectors. Alpha particles cause a current in the alarm. If smoke enters the detector, some of the alpha particles are absorbed and the current drops, triggering the alarm. o Thickness monitoring Long half-life beta emitters can be used for thickness monitoring of metal sheets. A source and receiver are placed on either side of the sheet during its production. If there is a drop or rise in the number of beta particles detected, then the thickness of the sheet has changed and needs to be adjusted.

Question 27

contamination what is it? what does it do? source? prevention? causes?

Answer 27

Contamination: Occurs when material that contains radioactive atoms is deposited on materials, skin, clothing, or any place where it is not desired. 1. object exposed to radiation t become radioactive 2. Irradiating a material does not make that material radioactive. However, it can kill living cells 3.source is from radiation emitted outside of the object 4.prevent by using shielding, such as lead clothing 5.caused by the presence of radioactive sources outside the body

Question 28

Alpha describe the dangers of ionising radiations, including: that radiation can cause mutations in living organisms, that radiation can damage cells and tissue, the problems arising from the disposal of radioactive waste and how the associated risks can be reduced.

Question 29

Beta describe the dangers of ionising radiations, including: that radiation can cause mutations in living organisms, that radiation can damage cells and tissue, the problems arising from the disposal of radioactive waste and how the associated risks can be reduced.

Answer 29

low-activity sources used in smoke alarms

Question 30

Gamma describe the dangers of ionising radiations, including: that radiation can cause mutations in living organisms, that radiation can damage cells and tissue, the problems arising from the disposal of radioactive waste and how the associated risks can be reduced.

Question 31

define nuclear fission

Answer 31

splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce energy. This is the method currently used in nuclear power stations

Question 32

define nuclear fusion

Answer 32

process where lighter atoms are forced to join together to make heavier atoms. This releases energy.

Question 33

what is radioactive decay

Answer 33

random process involving unstable nuclei emitting radiation to become more stable.

Question 34

nuclear fusion, nuclear fission and radioactive decay all can be sources of ________

Answer 34

energy

Question 35

explain the alpha decay process

Answer 35

1. heavy (helium) nucleus emits an alpha particle 2. nucleus changes to that of a different element

Question 36

explain the beta decay process

Answer 36

A neutron turns into a proton and emits a beta particle (electron) The nucleus changes to that of a different element

Question 37

explain gamma decay process

Answer 37

After a previous decay, a nucleus with excess energy emits a gamma particle. Gamma particles are a form of electromagnetic radiation.

Question 38

uses of radioactivity in medicine

Answer 38

o Sterilisation of equipment Gamma emitters are used to kill bacteria or parasites on equipment so it is safe for operations (this means they can be sterilised through their protective packaging to eliminate the risk of contamination). o Diagnosis and treatment - Short half-life gamma emitters such as technetium-99m are used as tracers in medicine as they concentrate in certain parts of the body. The half-life must be long enough for diagnostic procedures to be performed, but short enough to not remain radioactive for too long. - Other gamma emitters such as cobalt-60 can be used to destroy tumours with a high dose of radiation.

Question 39

irradiation what is it? what does it do? source? prevention? causes?

Answer 39

1. object exposed to radiation but does not become radioactive 2. Irradiating a material does not make that material radioactive. However, it can kill living cells 3.source is from radiation emitted outside of the object 4.prevent by using shielding, such as lead clothing 5.caused by the presence of radioactive sources outside the body

Question 40

what are the products of nuclear fission and what is released

Answer 40

the process of splitting a nucleusa uranium-235 nucleus absorbs a thermal (slow-moving) neutron, it splits into two daughter nuclei and 2 or 3 neutrons, releasing energy in the process.

Question 41

what can the products of nuclear fission do

Answer 41

neutrons then can induce further fission events in a chain reaction by striking other uranium-235 nuclei

Question 42

describe uses in a nuclear reactor : control rods moderator reactor

Answer 42

1. boron - absorbs neutrons and keeps number of neutrons that only one fission neutron per event goes on to induce further fission 2. water - slows down neutrons by collisions so they move slow enough to be absorbed by another u-235 nucleus 3. thick steel vessel - withstands high pressure and temperatures and absorbs some radiation. has concrete walls that act as radiation shields to absorb all radiation escaping reactor core

Question 43

define chain reaction

Answer 43

neutrons then can induce further fission events in a chain reaction by striking other uranium-235 nuclei

Question 44

how to dispose of radioactive waste

Answer 44

geographically stable, sealed in glass blocks in lead lined boxes, buried deep underground away from people as could leach into groundwater amd contaminate soil, rivers and drinking water

Question 45

explain process of nuclear fusion

Answer 45

the process of fusing two nuclei to form a larger nucleus, results in a loss of mass from smaller nuclei and release of energy

Question 46

explain process of nuclear reactor

Answer 46

substance pumped around reactor energy from fission transfers the energy to water by heating water into steam steam turns turbine turbine turns generator generator produces electricity

Question 47

how do sun and stars release energy

Answer 47

nuclear fusion

Question 48

why does nuclear fusion not occur at low temperatures

Answer 48

● Nuclear fusion does not happen at low temperatures and pressures because the electrostatic repulsion of the protons is too great.