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CHEMISTRY-FY > S1-L2 The structure of the Atom > Flashcards

S1-L2 The structure of the Atom Flashcards

1
Q

Outline the basic structure of an atom

A
  • Electrons (-)
  • Protons (+)
  • Neutrons (uncharged)
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2
Q

How big is the atom compared to the nucleus?

A

-atom diameter 10, 000x larger than that of its nucleus

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3
Q

What is the charge of an atom?

A
  • neutral

- -> e- loss gives charged ion

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4
Q

Briefly outline the nucleus of an atom

A
  • centre of atom- almost all mass there

- atom’s protons & neutrons compose it

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5
Q

Define the following terms:

1-Nucleons
2-Atomic number (Z)
3-Mass number (A)

A

1- protons and neutrons
2- n. of protons in nucleus of atom
-sum of protons and neutrons in nucleus
–>AKA nucleon number

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6
Q

Describe the electrons of an atom

A
  • surround nucleus–> occupy specific region in space-orbitals
  • orbitals grouped in to shells
  • ->identified by principle quantum number, n= 1, 2, 3…each shells contains unique set of orbitals
  • completely filled shell v. stable–> noble gas
  • e-s determine atom properties like reactivity AND bond forming ability
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7
Q

Define an isotope

A
  • atoms with same atomic number BUT different mass number
  • ->or same n. of protons BUT different n. of neutrons
  • different atoms of same element
  • same n. of protons as e-‘s
  • mass varies due to varying neutron number
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8
Q

Outline the following properties of isotopes:

1-chemical
2-physical

A

1- isotopes outer e- same AND same chemical identity so chemical properties identical
2-such as density can differ due to different mass of isotope

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9
Q

What is the “kinetic isotope effect”?

A

-heavier isotopes react slightly slower

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10
Q

What are the 3 main isotopes of hydrogen?

A
  • 1H- most abundant isotope
  • 2H- use in isotopic labelling experiments/ v. useful in NMR spectroscopy
  • 3H- radioactive–>used in labelling experiments
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11
Q

Outline the main isotopes of carbon

A
  • carbon-12 (6,6) stable
  • carbon-13 (6, 7) stable
  • carbon-14 (6, 8) radioactive
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12
Q

What are the isotopes of chlorine AND bromine?

A
  • chlorine: 35 Cl/ 37 Cl

- bromine: 79 Br. 81 Br AND 23+ more unstable isotopes

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13
Q

Define Relative atomic mass (Ar)

A

-of an element is weighted average of individual isotopes

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14
Q

Example: 35 Cl and 37 Cl

What are their mass number?

A
  • 35 Cl: P=17/ E= 17/ N=18
  • -> mass number is 35
  • 37 Cl: P= 17/ E=17/ N=20
  • ->mass number is 37
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15
Q

Outline the composition of an ordinary chlorine atom and it’s measured atomic weight

A
  • ordinary composition is 3 35 Cl atoms and 1 37 Cl atoms

- ->so measured atomic weight is (3 x 35) + (1 x 37)/ 4 = 35.5

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16
Q

What are “stable” and “unstable” isotopes?

A
  • Stable: remain unchanged indefinitely
  • Unstable: undergo spontaneous disintegration- to become stable nucleus
  • -> disintegration results in emission of small particles AND or radiation
  • also named as radioactive isotopes
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17
Q

Outline the use of the two types of isotopes mentioned above

A

-Can use both forms as diagnostic AND tracer tools in research

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18
Q

What is “mass spectrometry”?

A
  • measures molecular weight of atoms/ compounds via observation of m/z ratio of ions
  • works for both stable and unstable isotopes
19
Q

What are the applications of mass spectrometry and how does this occur?

A

-determining isotopic abundance AND identity of small molecules + proteins and more
-atoms + molecules converted in to ions which can separate into ions which can separate on basis of their masses AND motions in
magnetic/electrical field

20
Q

Example: Outline the features of the mass spectrum of neon-3 isotopes present

A
  • 20 Ne/ 21 Ne/ 22 Ne
  • peak position gives atomic mass
  • peak intensity–> gives relative abundance
  • normally highest abundance scaled up to 100%
  • -> other values adjusted accordingly
21
Q

Outline some of the uses of the following stable isotopes:

1- Ca-42, -44, -46, -48
2- C-13
3- Fe-54, -57, -58
4- O- 18

A

1-calcium metabolism/ bioavailability/ nutritional Ca role in pregnancy, growth AND development & lactation
2- molecular structure AND chemical reaction mechanism study
-molecular fingerprinting-dope testing athletes
3- metabolism/ energy expenditure studies
-metabolic tracer studies to identify genetic iron control mechanisms
4- studies of metabolism & energy expenditure
-lean body mass measurements
-obesity research

22
Q

Define the term “radioactive decay”

A
  • nucleus of unstable radioisotope seeks energetic stability by emitting particles/ radiation
  • -> alpha/ beta AND gamma particles
23
Q

What is “half life”?

A
  • t 1/2 (time to half) of radioactive isotopes

- -> time taken for activity set amount of radioactive substance to decay to half its original value

24
Q

Outline and briefly explain the following mechanisms of radioactive decay

1- Alpha (a) radiation

A

1- Alpha particle emission

  • helium nuclei
  • (+) charged
25
Q

2- Gamma (Y) Rays

A

2- Gamma photon emission

  • neutral
  • no effect on atomic mass/ number
  • often produced alongside a/ B particles- a or B decay leaves nucleus in excited state
  • -> then loses energy by Y emission
  • high frequency of EM radiation
26
Q

3- Beta (B) Radiation

A
  • 2 types:
  • -> beta (-) e- emission
  • -> beta (+) positron (anti-electron e+) emission
27
Q

What is the “capture process”?

A

-small particle collides with nucleus AND added to it

28
Q

Outline “neutron capture”

A

239Pu + 1–> 240Pu –> 241Am

94 0 94 95

29
Q

Describe the “boron neutron capture theory”

A

10 B + 1 n –> 7 Li + 4 He

5 0 3 2

30
Q

What is the radiation penetrating power of alpha/ beta and gamma radiation

A
  • alpha- cant penetrate past paper
  • beta- unable to penetrate past aluminium
  • gamma- unable to penetrate past lead
31
Q

What is “Xofigo”?

A

-isotope medication used to treat prostate cancer which spread to the bones

32
Q

Why is xofigo administered by injection?

A

-Half-life of Radium-223 in xofigo short so when patient injected Radium-223 able to quickly reach bone where cancer spread to

33
Q

Why is Ra suitable to treat bone metastasis?

A

-Radium-223 mimics calcium found in bones

34
Q

Which steps in decay chain of Ra-223 involve in alpha-emission?

A

6 steps:

1) Ra (223) –> Rn (219) –> Po (215)–> Pb (211)
2) At (215)–> Bi (211)–> Ti (207)
3) Po (211)–> Pb (207)

35
Q

Outline the application of unstable isotopes in the following categories:

1- Industrial

A

1- energy generation

  • food & medical supply sterilisation (usually 60 Co-Cobalt)
  • imaging AND gauging
36
Q

2- Medical

A

2- diagnostic

-therapeutic–> weakening/ destroying particular targeted cells

37
Q

3- Domestic

A

3- smoke detectors–> use 241 Am

38
Q

What is “imaging”?

A
  • Radioisotopes used for diagnosis must emit gamma rays of sufficient energy to escape from body
  • -> must have half-life short enough for it to decay away soon after imaging complete
39
Q

Outline the use of the following common radioisotopes:

1- 99^ Tc ^ m
2- thallium-201 chloride 
3- 82 ^Rb/ 99^Tc^m
4- 18^F -Fluoro-deoxy glucose (FDG) 
5-other 18^F- compounds
A

1- t 1/2 6 hours/ emit Y and low energy B particles/ produced on site in generator
2- myocardial perfusion imagine (MPI)
3- detection AND prognosis of coronary artery disease
4- often used for PET imaging which has half-life of 110 min–> to measure cell metabolism
5- image DNA synthesis AND hypoxia
–>condition where region of body deprived of O2 supply at tissue level

40
Q

Define and describe the term “therapy”

A
  • Selective damage to unhealthy tissue
  • radioisotope used for therapy should be strong B emitter to damage cells in small area
  • Y emission allows imaging too
41
Q

What is the application of radisotopes?

A

-can implant near tumor (brachytherapy)/ injected with selective uptake

42
Q

Outline the following commonly used radioisotopes for therapy

1-Radioiodine: 132^I/ 131^I
2- 89^SrCl and 153 Sm
3- 32^P
4- Lutetium- 177/ Yttrium-90

A

1- 132^I for diagnostics
131^I for overreactive thyroid/ thyroid cancer treatment
-131^I half life–> 8.02 days AND decays by B and Y emission
2- B emission t 1/2 1.93 day- bone metastasis (spread of cancer from original site to bone)
3- B emission AND half-life 14.28 days
–> control of red blood cell production in bone marrow in polycythemia vera
4- multiple uses- conjugated (reversibly combined substance) to peptide OR antibodies like Zevalin in sealed source brachytherapy (involves placing radioactive material inside body to treat cancer)

43
Q

Summary of lecture

A
  • Atom- comprised of nucleus (protons AND neutrons) & surrounded by e-‘s
  • isotopes- atoms of same atomic number BUT different atomic mass
  • stable + unstable isotopes
  • isotopes in medicine
  • mass spectrometry

CHEMISTRY-FY (11 decks)

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