L2 Atom structure & Isotopes Flashcards
What is a proteon?
The protons & neutrons
What is the atomic number?
No. of protons in the nucleus of an atom - allows the element to be identified.
What is the mass number?
Sum of the protons & neutrons in the nucleus
What is an orbital?
The specific region around the nucleus that e- occupy.
What is a shell?
Families that orbitals are grouped into - can be identified by the principal quantum no.)
What are isotopes?
= atoms with the same atomic no. but different mass no. = same no. of protons & different no. of neutrons.
- Chemically identical because they have the same outer e- & chemical identity
- Physical properties can differ
What is the kinetic isotope effect?
= heavier isotopes react slightly more slowly
What are the hydrogen isotopes?
- what are they used for?
H-1 = Protium - most abundant isotope H-2 = Deuterium - used in isotopic labelling experiments, very useful in NMR, safe substance H-3 = Tritium - radioactive, used in labelling experiments
What are the carbon isotopes?
- what are they used for?
C-12 - most abundant isotope
C-13 - useful in NMR
C-14 - used in radiocarbon dating as C-14 is accumulated in living tissue (stops once the sample is dead), C-14 decays at a steady rate so the quantity of it in a sample can be used to estimate age - forensic/archaeology
What are stable isotopes?
= Isotopes that remain unchanged indefinitely
What are unstable isotopes?
= Isotopes that undergo spontaneous decay in order to become a stable nucleus (this results in the emission of small particles/radiation)
= Radioactive isotopes
What is mass spectrometry?
= An analytical technique that measures the Mr of atoms/compounds by observing the mass to charge ration (m/z) of ions (the ions are separated on the basis of their masses & motions in magnetic or electrical fields)
- Works for both stable/unstable isotopes
- Applications: determining isotopic abundances, identify small molecules/atoms, biomarkers of disease, identifying if you have the desired/predicted product
What are the uses for stable isotopes: Calcium-42, -44, -46 & -48?
- Ca metabolism, bioavailability & absorption parameters during physical stress, bed rest & space flight
- Osteoporosis research & bone turnover studies
- Role of nutritional Ca in pregnancy, growth & development & lactation
- Bone changes associated with diseases such as diabetes and cystic fibrosis
What are the uses for Carbon-13?
- Elucidation of metabolic & bio synthetic pathways
- Noninvasive breath tests for research and diagnosis
- Molecular fingerprinting- dope testing athletes
What are the uses for Copper-63, -65?
Noninvasive studies of copper metabolism and requirements.
What are the uses for Helium-3?
In vivo magnetic resonance studies
What are the uses for Hydrogen-2?
- Vitamin research
- Chemical reaction mechanisms
What are the uses for Iron-54, -57, -58?
- Metabolism, energy expenditure studies
- Research to develop successful intervention for anaemia
- Metabolic tracer studies to identify genetic iron control mechanisms
What are the uses for Krypton-78, -80, -82, -84, -86?
Diagnosis of pulmonary disease.
What are the uses for Lithium-6?
- Na & renal physiology
- Membrane transport
- Psychiatric diseases
What are the uses for Nitrogen-15?
- Whole body protein turnover, synthesis & catabolism
- Amino acid pool size & turnover
- Metabolism of tissue and individual proteins
What are the uses for Oxygen-18?
- Studies of metabolism & energy expenditure
- Lean body mass measurements
- Obesity research
What is radioactive decay?
The nucleus of an unstable radioisotope seeks energetic stability by emitting particle/radiation: alpha, bet and gamma protons
What is half-life (t1/2)?
= the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
What is alpha radiation?
= the emission of a helium nuclei (4/2 He) = alpha particle & the original atom (proton no. -2, mass no. -4)
A/Z X -> 4/2 He + A-4/Z-2 Y
What is gamma radiation?
= the emission of a gamma photon (high-frequency electromagnetic radiation)
- Has no effect on A or Z
- Often produced alongside alpha or beta -> as when alpha or beta leave it leaves the nucleus in an excites state, it then loses energy by gamma emission
A/Z X -> 0/0 ϒ + A/Z X
What is beta minus radiation?
= the emission of an electron
- The product has a mass + 1
A/Z X -> 0/-1 e + A/Z+1 Y
What is beta plus radiation?
= emission of a positron (= anti-electron, same mass as an e-, but the opposite charge, +1)
- The product has a mass -1
A/Z X -> 0/+1 e + A/Z-1 Y
What is capture process?
= a small particle (e-, neutron etc) collides with the nucleus and is added to it
Neutron capture:
A/Z X + 1/0 n -> A+1/Z Y
Clinical applications: the atm that has ‘captured’ the neutron is very unstable so quickly decays
What is the penetrating power (what are they blocked by) of alpha, beta & gamma radiation?
Alpha: paper/skin
Beta: aluminium (may get in/out the body)
Gamma: lead
What are industrial applications of unstable isotopes?
- Energy generation
- Sterilisation of food & medical supplies (usually uses Co-60) - gamma radiation doesn’t damage like heat does
- Imaging & gauging
What are the domestic applications for unstable isotopes?
Smoke detectors using Am-241 - alpha particles can’t be detected in a small chamber because they bounce off the smoke
What are the medical (diagnostic) applications for unstable isotopes?
Diagnostic/Imaging
= a short half-life gamma isotope is used because they emit rays of sufficient energy to escape the body and have a half-life sort enough to decay once imaging is complete
1. Myocardial Perfusion Imaging (MPI): detection & prognosis of coronary artery disease and measurement of the uptake of a radio label in tumours that have poor bloody supply -> TlCl-201, Rb-82 & Tcm-99
2. PET: use F-18-Fluoro-deoxy glucose (FDG) -> measure cell metabolism and other F-18 compounds image DNA synthesis and hypoxia
What are the medical (therapy) applications for unstable isotopes?
Therapy = selective damage to unhealthy tissue
= a strong beta emitter is used to damage cells in a small area, gamma is also used for imaging
- Beams
- Needle/plates that are implanted in to tumours (more specific)
- Some elements are taken up by specific tissues e.g. iodine in the thyroid – targeted therapy
1. Radioiodine: I-132 for diagnostics; I-131 for treatment of overactive thyroid or thyroid cancer
2. Sr-89Cl & Sn- 153 bone metastasis (preferentially taken up by the bones)
3. P-3232P control of red blood cell production in bone marrow in polycythemia vera
4. Lutetium-177, Yttrium-90 - multiple uses; conjugated to peptides or antibodies eg Zevalin, in sealed source brachytherapy. – prostate cancer
