1.2: Atomic Structure Flashcards
What does Atomic Number (Z) represent?
The number of protons in the nucleus of an atom
What does Mass Number (A) represent?
Synonym?
The sum of protons and neutrons in the nucleus
(Also called nucleon number)
What do the outermost electrons determine?
- The properties of the atom
- Reactivity - the ability to form bonds
Define Isotopes
Atoms with the same number of protons but different number of neutrons
Same Atomic Number but different mass number
What are the 3 properties of isotopes?
- Same outer electrons
- Same chemical identity
- Physical properties can differ
What are the 3 isotopes of Hydrogen?
- Protium - 0 neutrons
- Deuterium - 1 neutron
- Tritium - 2 neutrons
What does mass spectrophotometry measure?
It measures the weight of atoms or compounds by observing the mass to charge ratio (m/z) of ions
What are the applications of mass spectrophotometry?
- Determining the abundance of isotopes
- Identification of small molecules and proteins
What does the height of peak and its position show you in mass spectrophotometry?
- Peak height gives relative abundance
- Positions of peaks gives atomic mass
Define ‘Relative Atomic Mass’
The weighted average of the individial isotpes
Can stable isotopes change?
NO!
They remain unchanged indefinetly
What are the 2 properties of unstable isotopes?
Synonym?
- They spontaneously disintegrate to become a stable nuclues
- Their disintegration results in emission if small particles and/or radiation
- They are also called radioactive isotopes
What can both, stable and unstable isotopes be used for in scientific research?
- Diagnostic tools
- Trackers
Give one application of stable isotope
H. pylori breath testing
Naturally occurring Carbon:
~99% Carbon - 12
1% Carbon - 13
Traces of Carbon - 14
What happens during radioactive decay?
The nucleus of an unstable radioisotope seeks energetic stability by emitting particle/radiation
- alpha
- beta
- gamma photons
What is the half life (t ½) of a radioactive isotope?
The time taken for the activity (of a certain amount of the substance) to decay to half the initial value
What happens in alpha radiation?
- An alpha particle is emissed
- The alpha particle = Helium nuclei
- Causes a positive charge
What happens in gamma radition?
- A gamma photon is emissed
- High frequency EM radiation
- Neutral, therefore atomic mass and mass number don’t t change
- Often happens with alpha or beta decay
Why does gamma decay often happen after Alpha and beta decay
Alpha and beta decay leaves nucleus in excited state - It then loses energy by gamma decay
What happens in the two types of beta radiation?
Beta minus - emission of an electron
Beta plus - emission of a positron (anti-electron)
What is the capture process?
Where a small particle (electron, neutron etc) collides with a nucleus and is addedto it
What can stop alpha, beta and gamma radiation?
Alpha - paper
Beta - Aluminuim (foil)
Gamma - thick lead
What are the 3 industrial uses of unstable isotopes?
- Energy generation.
- Gamma sterilisation - Cobolt - 60
- Imaging
What is the domestic use for unstable isotopes?
Smoke detectors - 241Am (americium)
What are the 2 medical uses of unstable isotopes?
- Diagnostic
- Therapeutic
What are the musts for radioisotopes used in diagnosis?
- Must produce gamma rays of sufficienct energy to escape from the body
- Should have a half-life short enough for it to decay away soon after imagining
What are the 2 common isotopes used in dignostic imaging , what are their half lives and what do they emit?
- 99 Tc m - 6 hours - emits gamma and low energy beta particles
- 18 F - 110 minutes - Positron emitter (Used in fluorodeoxyglucose (FDG) to measure cell metabolism)
In what 3 ways are unstable isotopes used in therapy?
• Beams of radiation
• Implanted sources (brachytherapy)
• Biologically targeted agents
Requires selective damage to unhealthy tissue
Natural uptake??????
- 131I - t1/2 8.02 days; β and emission - thyroid* 89SrCl and 153Sm - t1/2 1.93 days; β emission - bone metastasis* 32P - t1/2 14.28 days; β emission - bone marrow
Targeted therapy e.g. Zevalin - lymphoma
What is the Kinetic isotope effect
Where heavier isotopes react slightly more slowly
