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Chemistry Option D > Option D8 > Flashcards

Option D8 Flashcards

(69 cards)

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1
Q

What is special about unstable atomic nuclei?

A

They emit radiation

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2
Q

What does the stability of the atomic nucleus depend on?

A

Number and type of nucleons present, which vary from isotope to another

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3
Q

What leads unstable nuclei to become stable?

A

Due to unbalanced forces and excess internal energy

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4
Q

What is the name of the process known to form stable nuclei from unstable ones

A

Radioactivity

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5
Q

What are unstable nuclei also referred as?

A

Radionuclides

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6
Q

What is radioactivity?

A

The emission of energy and particles from the nucleus as an atom decays into a more stable form. The emissions are known as radiation.

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7
Q

What are natural radionuclides?

A

They occur in the environment in air, water, and soil. They include 235U, 3H, 40K, and 14C. All elements with Z = 84 (Po, polonium) and higher are naturally radioactive, which means they have no stable naturally occurring isotope.

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8
Q

What are induced or artificial radionuclides?

A

Nuclei that are made to be unstable through
procedures that usually involve bombardment reactions with neutrons or helium nuclei at great speed. Many radionuclides used in nuclear medicine are produced in this way.

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9
Q

What are the protons and neutrons within the nucleus made of?

A

Quarks that are arranged in sets of three, and changes in
their type gives rise to some forms of radiation

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10
Q

What are antiparticles?

A

Particles that have equivalent mass but opposite charges

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11
Q

What is an example of an antiparticle?

A

Positron is the antiparticle of an electron with the same mass but with a positive
charge.

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12
Q

How are gamma rays produced?

A

When particles and antiparticles collide,
mutual destruction occurs producing gamma rays

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13
Q

What may happen within a nucleus when a radionuclide decays into a more stable from?

A

-ejection of a neutron
-ejection of a proton
-the conversion of a neutron to a proton by ejection of beta particle
- the conversion of a proton to a neutron by ejection of positron
-release of gamma rays

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14
Q

What happens when there is a change in the number of protons when radionuclide is decaying?

A

The product is a different element from the parent radionuclide.

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15
Q

What are the main types of radiation?

A

Alpha, Beta, and Gamma

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16
Q

What is alpha radiation?

A

the ejection of particles from the nucleus that carry a charge of 2+ and have a mass of 4 atomic mass units. Alpha particles are equivalent to a nucleus of
helium and can be denoted Helium (superscript 4, subscript 2) or alpha sign (superscript 4, subscript 2)

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17
Q

What happens when alpha radiation is emitted?

A

Emission of an alpha particle causes the mass number of a radionuclide to decrease by
4 units and the atomic number to decrease by 2 units.

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18
Q

What is beta radiation?

A

The ejection of electrons from the nucleus. They are formed during the
conversion of neutrons to protons, so the mass number stays the same and the atomic number increases by 1 unit. Beta particles are electrons and so have negligible mass
and a negative charge. They are denoted as beta sign (0 superscript and -1 subscript)

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19
Q

What is gamma radiation?

A

The emission of energy as electromagnetic waves (or photons).

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20
Q

What is radioactivity known as?

A

Ionizing radiation

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21
Q

Why is radioactivity termed ionization energy?

A

It has enough energy to interact with an atom and cause the removal of electrons, so the atom becomes ionized.

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22
Q

How can radiation form free radicals?

A

By the release of electrons, even those which are not found on the outer shell

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23
Q

Why are the ionizing effects of radiation dangerous to living cells.

A

If came in contact with water, then the free radicals of H and OH would be produced, as well as the breakdown of the double helical structure of DNA

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24
Q

How do the different radioactive emissions differ?

A

Their ionization density

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25
What is ionization density?
The average energy released along a unit length of their track
26
Why do alpha radiations have the highest ionization densities?
Due to their +2 charge and large size, and so produce electrons closer to each other in a small region within cell.
27
What does the half life of radioactivity determine?
The rate of decay
28
What does the rate of decay depend on?
The nature of the radioactive substance
29
Which order to radioactive substances follow?
First-order kinetics
30
What is the rate expression for a reactant N?
rate = k[N]
31
How can the rate expression be integrated?
Page 909
32
What is the half life?
The time taken for the concentration of a reactant to decrease to one half its original value
33
What is special about the radioactive decay process?
It is constant
34
What does the half life of a radioactive decay process depend on?
Decay constant
35
What is the relationship between the value of half life and rate of radioactive decay?
Inverse relationship, Short half-lives indicate high rates of decay and vice versa
36
What is nuclear medicine?
The use of radiation in healthcare practice
37
In what medical areas is nuclear imaging important?
Radiotherapy in the treatment of disease as well as nuclear imaging in diagnosis of it
38
What is a way to conduct nuclear imaging?
Attaching a radionuclide, known as a tracer, to a biologically active molecule, making a drug called a radiopharmaceutical. This is then taken orally or by injection. The tracer allows the progress of the drug to be traced as it emits gamma rays from inside the body, which can then be detected by a gamma camera.
39
How do radiopharmaceuticals helps in diagnosis of disease?
Radiopharmaceuticals are designed to target a certain part of the body where there may be abnormality or disease.
40
How can disease be detected?
The tracer is attached to molecules such as glucose or iodine, and the medical practitioner can view different angles of the place of abnormality by identifying cold or hot spots which indicate low and high amount of isotopes taken up respectively
41
What is the radiopharmaceutical that is most widely used?
Technetium-99m
42
Why is Technetium-99m widely used?
* Its half-life is 6 hours, which means that activity in the body stays high for long enough for metabolic processes to be examined by scanning, but also decays quickly enough to minimize the exposure to the patient. * Its decay involves the release of gamma rays and low-energy electrons. Low-energy gamma rays escape the body and are accurately detected by the gamma camera. * Technetium is chemically versatile, so acts as a tracer by bonding to a range of biologically active substances. These are chosen according to the organ to be studied.
43
What is Positron Emission Tomography? (PET)
Type of scanner that gives three-dimensional images of tracer concentration in the body
44
How does a PET scan work?
The radionuclide contains a positron-emitting tracer and is injected into the patient’s body where it accumulates in the target tissue. Positrons are emitted from the tracer and these combine immediately with electrons, releasing energy as gamma rays. Detection of the gamma rays by a camera enables their origin to be precisely determined.
45
What is an example of a common tracer for the PET scan?
Fluorine-18, which is bonded to glucose in the radiopharmaceutical.
46
What is Magnetic Resonance Imaging (MRI)?
It is an application of NMR spectroscopy, and uses the fact that H atoms have a magnetic moment due to odd number of protons
47
How does a MRI work?
The presence of a strong magnet will lead to radio waves to generate electronic signals that can be decoded into three or two dimensional images
48
Why does MRI have a wide application in living tissue?
Due to abundance of H atoms in water which make up 70% of the body
49
What is special about the MRI?
The fat that it does not use any ionizing radiation which means that it is non invasive.
50
Where is MRI mostly used?
Cancer detection, diagnosis of soft tissue injury as well as monitoring degenerative diseases
51
How does cancer arise?
Cancer cells arise when normal cells lose their regulatory mechanisms for the control of growth and division, and are characterized as rapidly growing abnormal cells, often known as a tumor
52
Why are cancer cells sensitive to radiation?
The fact that they are rapidly dividing can make cancerous cells particularly sensitive to damage by radiation, as this radiation targets DNA which controls cells division
53
Why are normal cells not as affected towards the ionizing radiation?
Due to different rates of cell division
54
What is the goal of radiotherapy?
Radiotherapy treatments involve irradiating the area containing the growth, with the aim of controlling or eliminating the cancer
55
What are the different types of radionuclides used in radiotherapy?
Strong beta-emitters that also emit gamma radiation to enable imaging
56
What are some examples of radionuclides used in radiotherapy?
Lutetium-177 and yttrium-90 are widely used on the basis of their emissions.
57
What is external therapy or teletherapy?
When an external source of radiation is directed at the site of cancer in the body from a radioactive source, usually cobalt-60. This undergoes beta decay producing the stable product nickel-60. Page 913. This reaction also emits gamma radiation, which is penetrating and damaging to cells, especially cancer cells.
58
What is a linear accelerator?
A type of particle accelerator in which microwave technology is used to accelerate electrons, which are then aimed at a heavy metal target to produce high-energy X-rays which are precisely directed at the tumor.
59
What is gamma knife radiosurgery?
Tiny beams of gamma radiation are focused on a tumor from approximately two hundred cobalt-60 sources, causing a strong dose to be delivered at the site where the beams converge.
60
What is internal radionuclide therapy?
A radioactive material is taken into the body, either in solid form as an implant or as a liquid.
61
How does internal radionuclide therapy work?
An implant is introduced near the site of the tumour and left there for a period of time. It is usually a radioactive metal in the form of a wire, seed, or tube and is a gamma or beta emitter.
62
What are some examples of radioactive liquids?
-phosphorus-32 -strontium-89 -iodine-131
63
What is Targeted Alpha Therapy (TAT)?
Effective in the treatment of dispersed cancers, that is those that have spread beyond the original tumor, a process known as metastasis
64
How does TAT work?
Alpha radiating nuclides are attached to carriers such as antibodies and are directed towards biological target
65
Why are alpha radiating nuclides used?
-they have very high ionizing density and so a high probability of killing cells at the target -alpha particle radiation is short range and so minimizes unwanted irradiation of normal tissue surrounding the targeted cancer cells.
66
What is the radionuclide used in TAT?
Lead-212
67
What is Boron Neutron Capture Therapy (BNCT)
Is used particularly in the treatment of brain and neck tumors.
68
How does BNCT work?
First the patient is given a high dose of the non-radioactive isotope boron-10, which concentrates in malignant brain tumors. This is followed by irradiation with neutrons of sufcifient energy to be absorbed by the boron – this is the boron neutron capture. The reaction is accompanied by the emission of high-energy alpha particles, which are in position to kill the cancer cells in the tumor.
69
What are some common side effects to radiotherapy:
-fatigue -nausea -hair loss -sterility -skin reaction

Chemistry Option D (6 decks)

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