L2 Atom structure & Isotopes

Question 1

What is a proteon?

Answer 1

The protons & neutrons

Question 2

What is the atomic number?

Answer 2

No. of protons in the nucleus of an atom - allows the element to be identified.

Question 3

What is the mass number?

Answer 3

Sum of the protons & neutrons in the nucleus

Question 4

What is an orbital?

Answer 4

The specific region around the nucleus that e- occupy.

Question 5

What is a shell?

Answer 5

Families that orbitals are grouped into - can be identified by the principal quantum no.)

Question 6

What are isotopes?

Answer 6

= 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

Question 7

What is the kinetic isotope effect?

Answer 7

= heavier isotopes react slightly more slowly

Question 8

What are the hydrogen isotopes?

- what are they used for?

Answer 8

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

Question 9

What are the carbon isotopes?

- what are they used for?

Answer 9

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

Question 10

What are stable isotopes?

Answer 10

= Isotopes that remain unchanged indefinitely

Question 11

What are unstable isotopes?

Answer 11

= Isotopes that undergo spontaneous decay in order to become a stable nucleus (this results in the emission of small particles/radiation)
= Radioactive isotopes

Question 12

What is mass spectrometry?

Answer 12

= 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

Question 13

What are the uses for stable isotopes: Calcium-42, -44, -46 & -48?

Answer 13

• 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

Question 14

What are the uses for Carbon-13?

Answer 14

• Elucidation of metabolic & bio synthetic pathways
• Noninvasive breath tests for research and diagnosis
• Molecular fingerprinting- dope testing athletes

Question 15

What are the uses for Copper-63, -65?

Answer 15

Noninvasive studies of copper metabolism and requirements.

Question 16

What are the uses for Helium-3?

Answer 16

In vivo magnetic resonance studies

Question 17

What are the uses for Hydrogen-2?

Answer 17

• Vitamin research

- Chemical reaction mechanisms

Question 18

What are the uses for Iron-54, -57, -58?

Answer 18

• Metabolism, energy expenditure studies
• Research to develop successful intervention for anaemia
• Metabolic tracer studies to identify genetic iron control mechanisms

Question 19

What are the uses for Krypton-78, -80, -82, -84, -86?

Answer 19

Diagnosis of pulmonary disease.

Question 20

What are the uses for Lithium-6?

Answer 20

• Na & renal physiology
• Membrane transport
• Psychiatric diseases

Question 21

What are the uses for Nitrogen-15?

Answer 21

• Whole body protein turnover, synthesis & catabolism
• Amino acid pool size & turnover
• Metabolism of tissue and individual proteins

Question 22

What are the uses for Oxygen-18?

Answer 22

• Studies of metabolism & energy expenditure
• Lean body mass measurements
• Obesity research

Question 23

What is radioactive decay?

Answer 23

The nucleus of an unstable radioisotope seeks energetic stability by emitting particle/radiation: alpha, bet and gamma protons

Question 24

What is half-life (t1/2)?

Answer 24

= the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.

Question 25

What is alpha radiation?

Answer 25

= 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

Question 26

What is gamma radiation?

Answer 26

= 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

Question 27

What is beta minus radiation?

Answer 27

= the emission of an electron
- The product has a mass + 1

A/Z X -> 0/-1 e + A/Z+1 Y

Question 28

What is beta plus radiation?

Answer 28

= 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

Question 29

What is capture process?

Answer 29

= 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

Question 30

What is the penetrating power (what are they blocked by) of alpha, beta & gamma radiation?

Answer 30

Alpha: paper/skin
Beta: aluminium (may get in/out the body)
Gamma: lead

Question 31

What are industrial applications of unstable isotopes?

Answer 31

• Energy generation
• Sterilisation of food & medical supplies (usually uses Co-60) - gamma radiation doesn’t damage like heat does
• Imaging & gauging

Question 32

What are the domestic applications for unstable isotopes?

Answer 32

Smoke detectors using Am-241 - alpha particles can’t be detected in a small chamber because they bounce off the smoke

Question 33

What are the medical (diagnostic) applications for unstable isotopes?

Answer 33

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

Question 34

What are the medical (therapy) applications for unstable isotopes?

Answer 34

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