Complex Chemistry/ Nuclear Chemistry Flashcards
Radiation
Emission of subatomic particles or high energy electromagnetic radiation
Nuclear Decay
Integration in the nucleus. Continuous, spontaneous random process
Radioisotope/ radio nuclide
A nucleus that changes its structure spontaneously and continuously while emitting characteristics types of ration
3 types of emissions
Alpha/ Beta/ Gamma
Alpha emission
- Short range, highest ionization.
- Stopped by thin card, cannot penetrate skin, causes severe burn
- A decrease by 4, Z decrease by 2
Beta emission – 3 types:
Negatron Decay / Positron Decay/ Electron Capture
- Penetrate further than alpha, stopped by metal
Negatron Decay
- Emission of high speed, energetic e- or negatively charged beta particles
- Neutron to proton transition n > p + (-1e) + v (v = antineutrino)
- Z decrease by 1, A stay the same
Positron Decay
- emission of high energetic positively charged electrons (beta particles, antiparticle)
- Proton to neutron transition p > n + (+1e) + v (v = neutrino)
(Antiparticle meets corresponding particle = annihilation) - +1e + -1e > 2 gamma distinctive energy of 0.51 MeV
- Z decrease by 1, A stays the same
Electron Capture
- Proton to neutron transition p + (-1e) > n + x-rays
- Z decreases by 1, A remains the same
Gamma radiation
- Short wavelength, high energy electromagnetic radiation
- Very penetrating; stopped by thick lead plate or concrete shielding
- Emission of alpha and beta normally results in an excited state nuclide. Transition from excited state to ground state results in emission of gamma radiation
Nuclide
An atom of a particular isotope
Radioactive decay
Parent nuclide > daughter nuclide + nuclear radiation
Ratio of p+ & n0 change in parent nuclide > new elements formed
(p+ gives identity; e- gives personality)
Radioactivity
Unstable atom nuclei is spontaneously integrating and simultaneously giving out nuclear radiation
Chemical reaction vs Nuclear reaction
- Atoms are re- arranged to form new molecules in CR
- Different isotopes of the same element undergo same CR
- Different isotopes of the same element DO NOT all undergo the same NR
- Atoms are destroyed or created in NR
- Atomic mass change in NR
- Energy changes much greater in NR (E=mc^2)
Nuclear stability
Base on n:p ratio
Z < 20
stable ratio normally 1:1
Z > 20
1:1 to 1:1.5 is normally stable range
A > 209
major instability
Z > 83
instability
A > 238,
spontaneous fission
- Beta emission more likely for ______elements
- Alpha emission more likely for ______elements
Beta: lighter
Alpha: heavier
- Few nuclides with Z < 60 will emit _________
alpha particles
- Elements with_______Z number most abundant
- the only one of the 8 most abundant elements with odd Z number ?
an even Z number
Al
Nuclear Fission
the process of splitting the atoms
Nuclear Fusion
a nuclear reaction in which two or more atomic nuclei collide at very high speed and join to form a new type of atomic nucleus
Radioactivity half life equation
T(1/2) = 0.6931/ λ
Half - life
the time taken for half of the radioactive nuclei to decay.
Radioisotopes
Isotopes that are radioactive
Becquerel
- the activity of a quantity of radioactive material in which one nucleus decays per second
- 1 disintegration per second SI unit= 1 Bq
Activity =
- 1 Curie unit (Ci)
- the activity of 1g of pure (226) Ra= 3.7 x 10^10 Bq
Specific activity
activity per unit mass
Dosage is _____
2mSv per year - 20% own bodies, 30% cosmic/ space, 40% Radon, 10% medical exposure
Absorbed dose
amount of energy SI unit Gray (Gy). 1 Gy = 1JKg^-1
Rad
old unit of Gy for absorbed dose
1 Gy= 10 Rad
Dose equivalent measured in
Sieverts (Sv)
Old unit was Rem
1Sv = 100 Rem
Sv =
Gy x Q factors
Q factors
Biological effectiveness and must take into account type of radiation and types of tissues affected
Different tissues have different Q factors
alpha radiation has Q factor of _______
x 20 greater than either beta or gamma radiation
3 methods of detection & measurement of radioactivity in the environment
~ Geiger- Muller tube - ionisation of gases
~ Scintillation Techniques - excitation of liquids or solids
~ Dosimeters - induction of chemical change
Activity
no of nuclear disintegrations per sec (1 Becquerel= 1 disintegration/ second)
2 types of Radioactivity measurement
Differential - individual emissions per unit time - quantitative analytical work
Integral - total cumulative effect - dosimetry
For consistent radioactivity measuring results,_______
- background needs to be measured
- Significant number of measurements to be made - due to random nature of process of decay
- Statistical assessment of results required
Counting Efficiency (E)
Observed counts from detector/ activity from source
Factors affect E (__________)
Counting efficiency
- Geometrical position of counter wrt to source
- Absorption of radiation by any material between source and detector
- Limitations of detector
- Dead time losses
Measurements of Environmental Radioactivity
Measurement of radioactivity in water, air, many foods and animals done routinely
3 Environmental Radioactivity measuring method
Radiotracer methods
Activation Methods
Isotope Dilution Methods
Medical application techniques
- Positron emission tomography
- Single photon emission computed tomography (SPECT)
- Cardiovascular imaging
Nuclear medicine imaging is useful for detecting
- Tumors
- Blood cell disorders
- Inadequate functioning of organs
