C4 Flashcards
1
Q
What is the unit used for atomic masses called?
A
U, unified atomic mass unit.
2
Q
What is another representation of the unit U?
A
AMU, atomic mass unit.
3
Q
What is the symbol for the Relative Atomic Mass?
A
A
4
Q
Does the RAM have units?
A
No.
5
Q
Define Relative atomic mass.
A
the weighted average atomic mass of an atom taking into account all its naturally occurring isotopes relative to the mass of 1/12 of a Carbon-12 isotope.
6
Q
What can cause a mass spectrograph to be incorrect?
A
- percentage composition not adding up to 100%
- decimals in isotopic mass (unless atomic mass is decimal)
7
Q
What is ionising radiation?
A
Radiation that has sufficient energy to remove electrons from atoms.
8
Q
What is the result of ionising radiation?
A
Atoms are turned into ions (free radicals- a type of unstable molecule) which will readily react with nearby atoms, hence changing the molecule.
9
Q
What are some examples of ionizing radiation?
A
Ultra violet, x-ray, gamma ray
10
Q
Rate permeability of alpha particle, beta particle, and gamma rays
A
- alpha
- beta
- gamma
11
Q
What are some examples of background radiation?
A
Inhaled radionuclides, terrestrial radiation, chest x-ray, cosmic radiation
12
Q
What are the 4 results of damaged body cells and their related consequences?
A
- Repaired
- Dies and excretes
- Cancerous-> organ function impaired-> radiation sickness, death
- Organ function-> radiation, death
13
Q
Describe the stages of DNA damage
A
Damage passes: parent atom-> daughter atom-> hits DNA (nucleus)-> DNA breaks-> becomes a cancer cell-> cell growth-> becomes a tumor
14
Q
Describe the motion of alpha, beta, gamma with presence of magnetic field and why.
A
Alpha source leans towards magnetic field, beta against, gamma straight.
This is because of the charges the particles each have, where the positive and negative sides of the magnetic force repels identical forces.
15
Q
Describe the properties of alpha particle. (SNRCMIP)
A
Ejected from the parent nucleus
Helium nucleus
4/2 He; 4/2 a; 4/2 He^2+
Charge of +2
Mass of 4 u
Highly ionizing
Low penetration
16
Q
What has to be balanced in nuclear equations?
A
Number of protons and nucleons
17
Q
Describe the properties of beta decay. (SNRCMIP)
A
- Ejected from the nucleus
- ## 0/-1e ; 0/-1B
18
Q
How does the decay chain work?
A
Often radioisotopes decay into another unstable isotope which decays further
19
Q
What forms a stable ion?
A
- full valence shell
- lowest energy state
20
Q
What is an UNSTABLE nuclei?
A
When the neutrons and protons in the nucleus aren’t held together strongly.
21
Q
What happens to unstable isotopes of elements? And what are they called?
A
They decay to form other elements, becoming a radioactive isotope/ or radioisotope.
22
Q
What is the energy emitted by radioactive substances called?
A
Nuclear radiation.
23
Q
What are the 3 different types of nuclear radiation?
A
Alpha particles, beta particles, and gamma rays.
24
Q
What are alpha particles?
A
Helium nuclei that contain 2 protons and 2 neutrons.
25
What are the charges of alpha particles, beta particles, and gamma rays?
A: 2+
B: 1-
C: neutral
26
Compare penetration of the 3 nuclear radiation and what can they be stopped by.
A: low penetration therefore cannot travel easily through materials, can be stopped by paper, few inches of air, or human skin
B: medium penetration therefore can penetrate human skin and damage living tissue, but cannot penetrate thin layers of plastic, wood, or aluminium
G: highly penetrating and cause serious permanent damage to living tissue. Can be stopped only by a thick shield of lead or concrete.
27
Can alpha particles damage the body?
Little hazard to the external body but can cause serious damage if breathed in, eaten, or injected.
28
Compare the speed of the 3 nuclear radiation.
Alpha: extremely slow, 5-7% of the speed of light
Beta: can travel at speed as high as 99% of the speed of light
Gamma: speed of light
29
Compare the size and mass of the alpha particles and beta particles.
A: 4u
B: negligible mass
30
What are gamma rays?
Bursts of energy released after alpha or beta particles are emitted.
31
Define half-life
The time taken for half of all the nuclei in a sample of a radioisotope to decay.
32
How long can half-lives be?
From a few microseconds to billions of years.
33
How are radioisotopes used in medicine?
Used as radioactive tracers to follow the movement of substances through liquids.
34
What do columns of the periodic table represent?
Elements with similar properties because they have the same arrangement of valence electrons.
The number of valence electrons is equal to the column number the element belongs to.
35
What do periods of the periodic table represent?
Contains elements with the same number of shells.
36
Which shell has lower energy- outer or inner?
Inner
37
Which elements have a full valence shell? Describe their radioactivity.
Noble gases, they are chemically unreactive/ stable
38
Why do other elements change their amount of electrons?
Other elements give up, gain or share electrons to achieve a full valence shell, in order to achieve a low energy state.
39
Why does atomic radius increase/decrease?
Atomic radii decrease across each group due to the increased amount of protons in the nucleus.
- valence electrons are attracted to the protons in the nucleus
- increased number of them increases the attraction and therefore contracts the radius.
Atomic radii increase across each period due to the increasing shell.
- valence electrons are now in a new, more distant electron shell
- increases shielding/ repulsion from inner shell electrons (increasing number of core electrons shield the valence electrons from charge in the nucleus)
- valence electrons are further away
- radii is larger
40
How is it possible for an atom to still remain on earth if it decays super quickly?
It is produced as the daughter isotope in other decay
chains.
41
What is meant by a chain reaction?
The neutrons produced from one fission reaction
start more reactions.
42
What is the decay equation?
N=N0*(1/2)^n
43
The counts are due to background radiation. What is meant by this and what causes it?
- due to natural radioactivity in the earth and air
- Radioactivity in the air is caused by cosmic rays from outer rays, as well as radioactive dust from nuclear explosions.
44
Why do counts of background radiation vary?
Radioactivity is a random process so the counts recorded in one minute may not be the same as in the next minute. It is impossible to predict when a count will be recorded- this is why an average is taken.
45
What is an isotope?
A type of atom of an element. It contains the same amount of protons but different number of neutrons, hence a different atomic mass.
46
What happens to a decayed element?
It changes to another element. However, the new element is also radioactive, it will decay into another radioactive element. The decay series continues until a stable element is formed.
47
How does the electron structure relate to potassium's position in group 1 and period 4?
Group 1 – 1 electron in the outer shell
Period 4 – 4 occupied electron shells
48
The shaded column of the early periodic table from 1865 does not correspond with a group in the modern periodic table. Identify how the properties of this group are inconsistent with the modern periodic table with reference to one physical property and the valency of the elements in this group.
- Elements in modern PT have similar physical
properties, but in the shaded column of the 1865
periodic table Fe conducts electricity, whereas oxygen
and sulfur do not.
- Modern PT elements in same group have same valency, whereas valency of iron is (+)2 or (+)3 and S and O are both (-)2.
- Other possible physical properties could have been
discussed e.g. MP, BP, lustre, malleability, ductility
49
Explain why there is a small decrease in the atomic radius between Z=8 (oxygen) and Z=9 (fluorine), but a large increase in the atomic radius between Z=9 and Z=11(sodium).
- Atoms of F (Z= 9) and O (Z = 8) each have 2
occupied electron shells.
- F has one more proton in the nucleus compared with O.
- Therefore, the valence electrons are attracted to the
nucleus by electrostatic forces more. So, F atom is a bit smaller than O atom.
- From 9 (F) to 11 (Na) there is an extra, occupied
electron shell, making the radius of the atom larger.
- This extra shell also reduces the electrostatic attraction between the nucleus and the valence electron hence Na is much bigger.
50
Rewrite the symbols for a proton and an alpha particle to better reflect the exact chemical nature of these particles.
4/2He^2+
1/1H^+
51
Justify that the terms hydrogen ion and proton can be used interchangeably.
1H
1
contains 1 proton in the nucleus and 1 electron. When it loses an electron it becomes a positive ion, H+ and consists of 1 proton.
52
Alpha particles are highly ionizing. Explain why with reference to how an alpha particle ionizes an atom.
An alpha particle has a (2+) charge so it needs to gain 2 electrons to become a stable He atom.
When it comes near an oxygen atom, for example, the particle will cause one of O's electrons to be detached and O will become O+, i.e. the O atom is ionised.
53
Rate ionization of the 3 types of radiation.
1. Alpha- can easily knock electrons off any atoms they collide with
2. Beta- Moderately ionizing
3. Gamma- Weakly ionizing
54
Where does the 'M' go in metastable elements?
Next to mass of original element. (undecayed)
55
Both isotopes of iodine-131 and iodine-123 can be used as radiotracers. Outline the similarities and differences in the atomic structure of these isotopes.
Both have the 53 protons and electrons in a neutral
atom. Iodine-131 has 78 neutrons and iodine-123 has
70 neutrons in the nucleus.
56
Iodine- 123 decays by gamma emission. Which of the two isotopes (123 and 131-> beta decayed) would be safer for the patient? Justify your choice.
I-123 would be safer for patient.
Beta particles are more strongly ionising than gamma.
Ionisation causes mutations to DNA which can cause
cancer.
57
2021 pp q5b
background, av count/30,
58
Explain the results of the experiment, with reference to the difference between radiation from a phone and nuclear radiation.
Mobile phones produce non-ionising electromagnetic radiation not nuclear/ionising radiation thus the GM counter
detected nothing.
59
State a type of radiation emitted by 99m
43Tc
Gamma
60
Explain why magnesium has a relative atomic mass of 24.31, but no single isotope has this mass.
The Ar(Mg)= 24.31 represents the weighted average of the mass numbers of the stable isotopes of magnesium (24Mg, 25Mg, 26Mg) and takes into account the relative abundances of these stable isotopes.
61
Write the formula of the likely anion of astatine.
AT^-
62
Explain why alpha particles are dangerous to humans whereas mobile phone radiation is not .
Because alpha particles emit ionizing radiation that can harm humans by causing DNA mutation in nearby cells, possibly forming cancer. Where lower energy microwave electromagnetic radiation of mobile phones is not believed to be harmful or ionizing to humans.
63
In the first week after a nuclear explosion or accident, neptunium-239 is one of the main hazardous radioisotopes found in the atmosphere. What properties of this decay contribute to neptunium-239 being dangerous?
The danger is caused by the beta radiation which is ionizing radiation. As plutonium-239 is a decay product, it is highly toxic too.
- The half-life is 2.3 days, therefore the beta radiation will decrease to approx 1/8th of the original activity during one week.
- But Pu remains a major hazard.
64
2020 pp Q4d
A sample of air was analysed in 1950 and found to contain small concentrations of each of the Use
isotopes listed in the table on page 6.
(d) If an identical sample of air was collected and sealed in 1950, and then stored at room temperature until 2020. Which isotopes, if any, would be present in detectable amounts? Explain. (2 marks)
table in photos
In 70 years neither 235 Np nor 239 Np would be detectable due to the v. large no, of half-lives since 1950. However 236 Np and 237 Np would have approximately the same activity as measured in 1950 because 70 years is a tiny fraction of their half-lives.
65
What would be the effect, if any, on the isotopic mixture present in 2020 if the sealed container of radioactive substance had been stored in liquid nitrogen (-196 degrees celsius)?
Temperature does not affect nuclear stability, therefore cooling to -196 degrees would have no effect on the decay rates.
66
Carbon-14 is formed when cosmic rays interact with nitrogen-14 in the atmosphere. Cosmic ray
activity has changed at various times in Earth’s history.
If the cosmic ray activity was high when the ancient bone was formed, explain the effect this would have, if any, on the estimated age of the ancient bone.
2020 pp q5a
If originally it contained more than 10*10^-11% of C-14, it would have taken longer to decay to 1.2*10^-11%, therefore sample would be older than predicted.
67
Name 2 other sources of background radiation (can't be cosmo)
Terrestrial radiation, inhaled nuclides.
68
Explain why background radiation must be considered in an analysis of isotope radioactivity.
True activity levels of isotopes must be corrected by subtracting the background radiation count from actual measured activity counts for precise results of the radioactivity of the isotope.
69
Hydrogen has three isotopes: 1/1H, 2/1H, and 3/1H. Describe the similarities and differences between these three isotopes.
- same no. of protons- 1 proton
- different no. of neutrons
- same no. of electrons
70
2/1 H and 3/1 H can undergo "nuclear fusion", where the two isotopes combine to produce an alpha particle and another particle. Complete the nuclear equation below for this process and name the other particle that is produced.
2/1 H + 3/1 H ->
4/2 He + 1/0 n
neutron
71
A laboratory technician measured the activity of a sample of sodium-27 at 9:00 a.m. to be 400 Bq. At 3:00 pm on the same day the reading had dropped to 100 Bq.
(a) Explain what is meant by an “activity of 400 Bq”.
400 nuclear decays per second
72
A laboratory technician measured the activity of a sample of sodium-27 at 9:00 a.m. to be 400 Bq. At 3:00 pm on the same day the reading had dropped to 100 Bq.
(b) What would the expected reading be at 9:00 pm on the same day for this sample?
9pm is 6 hrs after, half life is 3 hrs
N=N0 * (1/2)^4
= 400 * (1/2)^4
= 25 Bq
73
In 2006, a former Russian secret agent, Alexander Litvinenko died of radiation sickness after being poisoned with polonium-210; it was reportedly put into his cup of tea. Po-210 is highly
radioactive and decays by alpha emission. The activity of the amount ingested by Litvinenko was around 2.1 GBq (gigabecquerel)
(b) Explain how the assassin could safely carry the polonium-210 until they placed it into Litvinenko’s tea.
- alpha particles= low penetration
- could possibly carry it holding in his hand (radiation most stopped by dead skin cells)
- safer in briefcase/ bag
74
In 2006, a former Russian secret agent, Alexander Litvinenko died of radiation sickness after being poisoned with polonium-210; it was reportedly put into his cup of tea. Po-210 is highly
radioactive and decays by alpha emission. The activity of the amount ingested by Litvinenko was around 2.1 GBq (gigabecquerel)
(c) Explain why the assassin was not adversely affected by the radiation when they placed it into Litvinenko’s tea, whereas Litvinenko died from its effects. Give at least two reasons.
(3 marks)
- A can limit exposure time
- L has ingested it-> long exposure
- A exposed externally-> damage to dead skin cells
- L exposed internally-> damage to live stomach cells, etc
75
What has to be included in the symbol of an element/ isotope?
Atomic mass
Atomic number
Chemical symbol
Charge
76
(b) Which is larger, an oxygen or a fluorine atom? Explain.
- O larger
- Same amount of cells but F has one additional proton
- increasing electrostatic attraction force
- pulling valence shell tighter towards nucleus
- therefore smaller radius
77
(c) What atomic characteristics do the elements in group 17 have in common?
All have 7 valence electrons.
78
(a) Draw the Bohr model of an 17𝑁 atom.
(2 marks)
All shells drawn, shows components of nucleus (7P, 10 N)
79
(d) By comparing the properties of alpha particles, beta particles and neutrons, explain why neutrons are more effective in initiating a fission reaction than either alpha or beta particles. (2 marks)
0/1n+ 235/92 U -> 152/60 Nd+ ______+4*1/0 n
- alpha particles would be repelled by the positive charge in the U nucleus
- beta particles would be repelled by the surrounding electrons (and are fast moving)
- nucleus, with no charge, penetrate to the U-235 nucleus
80
Mango seed weevils are a pest that lay their eggs
just under the skin of green mangoes. If allowed
to hatch, the weevil lavae burrow into the ripe
fruit and grow within the mango seed. Nuclear
radiation is used to kill the weevil eggs as the
mangoes are packaged for export.
The table below gives information about 5
radioisotopes.
Isotope Half-life Radiation emitted
Caesium-134 2.1 years Beta
Cobolt-60m 5.3 years Gamma
Curium-242 160 days Alpha
Strontium-90 28 years Beta
Technetium-99m 6 hours Gamma
Which of these isotopes is the best choice to irradiate the mangoes with? Explain why you
chose this one, and what was wrong with the other radioisotopes.
- need to penetrate mango skin so alpha particles are not appropriate
- gamma rays will mostly travel right thru the mango, causing little ionisation and kill few weevil eggs
- beta radiators will kill eggs as they will penetrate the skin and have medium ionising power
- Sr-90 has longer halflife, therefore lasts longer
OR
- Co-60m has shorter half life, therefore more radioactive
81
A single carbon 12 atom has a mass of 1.993 x 10^-23 g. It has a relative mass of exactly 12 atomic mass units.
a) The weighted mass of a chlorine atom over its two isotopes is 5.888 x 10^-23 g. Show that its relative atomic mass is 35.45.
(5.888 x 10^−23/ 1.993 x 10^−23) x 12
5.888 x 10^-23/ 1/12 x 1.993 x 10^-23
82
What dangers exist for a patient that has been injected with a radioactive isotope, ne it an alpha or beta emitter?
Radioisotopes in the body will kill/mutate health
normal cells (via ionisation).
83
Write a decay equation for the formation of Os- 188 via beta decay.
188/75 Re -> 0/-1 e + 188/76 Os
84
2022 pp q2b
Account for the variation in the decay rate from the expected trend line.
Random nature of radioactivity
85
Lithium readily forms a stable Li+ ion. Why is Li+ the most stable ion?
Li has a full valence shell.
86
Two other elements near lithium on the periodic table are beryllium and boron. Which of the three elements has the smallest radius? Justify your wording.
- Boron
- All are in the same period and have the same number of occupied electron shells.
(or the valence shell is the same shell number)
- B has the highest nuclear charge and greatest force of attraction holding the valence electrons
87
0/1𝑛 + 235/92𝑈 → 152/60 Nd + 80/32G e + 4 0/1 𝑛
(b) Using the equation in part (a), explain how nuclear fission may become ‘uncontrolled’.
- Neutrons released as a byproduct may continue to react as a reactant of a new fission reaction
- if the 4 product neutrons interact with 4 other U-235 and repeats -> 4,16,64..., a self sustaining chain reaction is formed and it is explosive
- continues until no neutrons are produced in the fission reaction
88
Bohr model
- shows number of protons and electrons in the middle
- electrons circling the nucleus
89
Plum pudding model
- first sub-atomic particle of electrons discovered
- a sea of electrons with an equal amount of positive particles within
- JJ Thompson
90
Briefly explain Ernest Rutherford's experiment.
- made an extremely thin sheet of gold and shot alpha particles (helium nuclei) at it.
- if the plum pudding model was true, particles would only be deflected at a small angle
- however, it was wrong as not all but some were deflected at a huge angle
- suggesting that most of an atom is empty (thus most alpha particles missed the nucleus) and that the positive particles are actually concentrated in the centre
91
Strong force, what happens when it's not strong enough?
The force that holds together the atomic nucleus
- nuclear breaks apart shooting out particles resulting in radioactivity
92
what do you show in an electron shell diagram?
Number of electrons, element name
*NO NEED NUMBER OF NUCLEONS
93
What do u show in a lewis diagram?
Element name and sketch out number of valence electrons
94
What do groups and periods show on the periodic table?
Each Group (column) contains elements with similar properties because they have the same arrangement of valence electrons
Each Period (row) contains elements with the same number of shells
95
describe energy levels in electron shells and why.
Inner shells= low level
Outer shells= higher level
it requires energy to stay attracted to the nucleus. there is a stronger attractive force closer to the nucleus, thus inner shells have a low energy level because there's already a nice fat force keeping it attracted.
96
Describe what sub-critical mass is.
A subcritical mass is a quantity of fissile material (such as uranium or plutonium) that is not sufficient to sustain a self-sustaining nuclear chain reaction.
97
How to control a chain reaction?
control rods in reactor that determine how much heat it produces, can cease reaction by fulling inserting them into reactor.
- they end up absorbing the extra neutrons so there is no way for the chain reaction to continue and the reaction stops
98
What holds subatomic particles together?
Electrostatic forces.
99
what are some common examples of natural and artificial isotopes?
Natural Isotopes:
Carbon-12 (¹²C): This is the most common isotope of carbon, making up about 98.9% of all carbon on Earth.
Carbon-14 (¹⁴C): This is a radioactive isotope of carbon and is used in radiocarbon dating to determine the age of ancient organic materials.
Hydrogen-1 (¹H): The most common isotope of hydrogen, also known as protium, is by far the most abundant element in the universe.
Uranium-238 (²³⁸U): A natural isotope of uranium, it is used as a fuel in nuclear reactors.
Potassium-40 (⁴⁰K): A radioactive isotope of potassium, it's used in the potassium-argon dating method to determine the age of rocks.
Deuterium (²H): An isotope of hydrogen with one proton and one neutron, it is used in heavy water (deuterium oxide) and as a moderator in some nuclear reactors.
Artificial Isotopes:
Technetium-99m (⁹⁹mTc): This artificial isotope is used in nuclear medicine for various diagnostic imaging procedures.
Plutonium-239 (²³⁹Pu): An artificial isotope used in nuclear weapons and as a fuel in some nuclear reactors.
Iodine-131 (¹³¹I): An artificial isotope used in nuclear medicine for diagnosing and treating thyroid disorders.
Cobalt-60 (⁶⁰Co): An artificial isotope used in radiation therapy for cancer treatment and as a radiation source for industrial applications.
Curium-244 (²⁴⁴Cm): An artificial isotope used as a heat source in radioisotope thermoelectric generators (RTGs) for space missions.
Americium-241 (²⁴¹Am): An artificial isotope used in household smoke detectors and industrial devices that measure the thickness of materials.
100
Chlorine has two isotopes, cl-35 and cl-37. From the relative atomic mass, calculate the percentage of each isotope present in naturally occuring chlorine.
Relative atomic mass= cl-35
cl-35= 77.5%
cl-37= 22.5%
101
another method for treating different tumours involves injecting a beta emitter into the patient, forming the isotope osmium-188 (188 76 Os)
Write a decay equation for the formation of Os-188 via beta decay.
188 75 Re-> 0 -1 e+ 188 76 Os
102
Both alpha and beta radioimmunotherapy are very effective at killing tumours. Considering the ionisation and penetration of alpha and beta radiation, outline the advantages of each treatment. (4 marks)
Alpha:
Highly ionising, poorly penetrating.
Kills tumour cells effectively but only over a very
short range, so unlikely to kill large tumours.
Beta:
Less ionising, more penetrating.
Less effective at killing cancer cells but will kill to
greater depth, meaning it may be effective with large
tumours.
103
both isotopes of iodine-131 and iodine-123 can be used as radiotracers. Outline the similarities and difference in the atomic structure of these isotopes. (2 marks)
Both have the 53 protons and electrons in a neutral
atom. Iodine-131 has 78 neutrons and iodine-123 has
70 neutrons in the nucleus
104
write the decay equation for metastable Br-82.
(same thing but with gamma ray)
105
In industry, radiotracers can be used to detect water leaks in underground pipe systems. Tracers are put into the water, and after a few hours leaks can be detected by increased amounts of radiation in a specific location.
An isotope used for this purpose is metastable bromine-82, which decays by gamma emission and has a half-life of 35 hours.
Explain why this isotope is a good choice for this purpose. (2 marks)
Any two of the following were accepted:
Br 82 produces gamma radiation, which is able to
penetrate through the many metres of dirt to be
detected above ground.
It has a half-life long enough to allow for the buildup of
radiation to be detected, but short enough that it will
not be maintained the long term.
Gamma radiation is weakly ionising, therefore, as this
water may be ingested by people in their houses this is
the safest type of radiation to use.
106
define the term atomic number and why is it used for arranging the elements in the modern periodic table?
Atomic number is the number of protons in the
nucleus of an atom
It is unique to an element.
Or no two different elements have the same atomic
number, unlike RAM
107
The data points are joined to highlight that the graph above is not completely smooth
and some variation is present, particularly after 300 hours. What caused this variation
in activity?
Decay is random. At low counts, variations is more obvious.
108
Identify the difference between background radiation and other types of radiation, for example, mobile phones and fluorescent lights. (1 mark)
microwaves (phone) and visible light are non-ionising, having much less energy than background radiation.
109
Nuclear reactors are present in many countries around the world. A fuel for nuclear reactors
is uranium-235 and the reaction taking place is termed a fission reaction.
(a) Write a nuclear equation for the fission of uranium-235 via bombardment with a neutron
producing two different elements, one of which is barium-139, and three neutrons.
235/92 U+ 3 1/0 N-> 139/56 Ba + 94/36 Kr + 3 1/0 N
110
tasc 17
By including a diagram of uranium fission, explain what is meant by a nuclear chain
reaction. (2 marks)
photos
111
discuss the implication of having controlled or uncontrolled nuclear chain reactions.
- uncontrolled chain reactions release large amounts of energy in a short time-> explosion bomb
- controlled is used for nuclear power
112
The radioisotope 99 decays to produce 99m
42Mo 43 Tc
(ii) Write a balanced nuclear equation for this decay process. (1 mark)
99/42 Mo—> 99/43 Tc^m + 0/-1e + v
113
What is the significance of the m in 99/43 Tc^m?
m represents meta stable state where the nucleus is in an excited state and will emit gamma rays to achieve a lower energy and identical isotope of the same amount ie 99/43 Tc^m —> 99/43 Tc + gamma
114
(c) The half-lives of the radioisotope 99/42 Mo and 99/43 Tc^m are 67 hours and 6 hours
respectively. ANSTO, the nuclear facility based at Lucas Heights, exports 99/42 Mo for medical imaging all over the world.
(i) Suggest two reasons why ANSTO does not export
99 m
43Tc . (2 marks)
With such a short half life of only 6 hours there would be so little of the 99/43 Tc^m remaining after a delivery period of say 1 day (ie only 1/16th remain)
115
Patients treated with radioisotopes are advised to avoid close contact with children or
pregnant women for a 24-hour period.
Activity after 15 hr= 1.8 Mbq (half life= 6hr)
(iv) Explain the basis for this precaution. (2 marks)
The patient will be emitting gamma radiation from within their body as the activity will still be about 0.6 MBq even after 24 hr. This radiation may cause harm to persons within close range, ie cell damage due to ionising radiation.
116
Imagine you are a doctor in a nuclear medicine department where a beta emitter is used.
Explain the three main ways in which you can minimize your exposure to this type of radiation in this situation. (3 marks)
Limit exposure time with automated testing.
Install shielding in walls and around the source, stay away from fam, wear lead infused apron
Increase distance from patient undergoing therapy by leaving room during patient exposure.
117
Imagine you are a doctor in a nuclear medicine department where a beta emitter is used.
Would you change your procedures if you had to deal with a gamma emitter?
Yes.
Gamma has greater penetration power so more dense shielding needed.
118
Exposure to nuclear radiation can cause radiation sickness in the short term, and cancer in the long term. Explian how radiation can cause both these problems. ( 4 marks)
Radiation sickness:
- large dose in short time
- many cells killed/ damaged
- organ function impaired
Cancer:
- a single cell has mutated
- replicates over time
- forms a tumour
