17. World Of Isotopes Flashcards
What are radioisotopes?
Mother nuclides disintegrate to daughter nuclides at a given half-life
When they decay, there’s energy release/ radiation
What are stable isotopes
Disintegration has not been observed yet
All visible matter is made up of stable isotopes
What are two types of isotopes?
Radioisotope and stable isotope
Describe Isotopes, Isobars, Isotones
Isotope- same proton number, different mass number and neutron number
Isobar- same mass number, different proton number and neutron number
Isotones- same neutron number, different proton and mass number
Describe the chart of nuclides
Each line represents an element
Each square represents an isotope
Color represents mode of decay
Radioisotopes are more common than stable isotopes. True or false
True
Define atomic weight
Atomic weight of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of an atom of Carbon-12
Define standard atomic weight
IUPAC’s recommend for the element
What are mononuclidic and polynuclidic elements?
Made up is a single stable isotope
Standard atomic weight equals mass of the isotope
Poly- blend of up to 8 stable isotopes
Standard atomic weight = sum of nuclides masses WEIGHTED by the abundances of individual isotopes
Define mass defect
Mass of nucleus is less than mass of individual protons and neutrons nuclear fusion: difference in mass is released as energy
Define the Oddo-Harkins rule
Elements with an even number of protons (eg C) are mostly abundant than elements with an odd number of protons (eg N)
Nitrogen (Z=7) is more abundant than Carbon (Z=6). T or F
False. Even more
All isotopes with Z>= 83 are unstable. T or F
True
All elements with Z<= 82 are unstable. T or F
False. All elements with Z<= 82 have at least one stable isotope
Describe the valley of stability
defined by the right ratio of neutron to proton
radioisotopes try to reach the valley of stability through radioactive decay
mode of decay depends on neutron to proton ratio
Describe Alpha decay
emission of alpha particle=helium nucleus
Z>83
238U - 234Th + 4He
92 90 2
Describe Beta decay
neutron to proton
40K = 40 Ca + e- + v
19 20
Describe Positron decay (beta decay)
proton to neutron
40K = 40 Ar + e+ +v
19 18
Describe electron capture
inverse Beta decay
40K + e- = 40Ar
19 18
Describe gamma rays
no form of decay = does not affect the atomic mass and number
occurs with other forms of decay
discrete energy, characteristic for nuclide
Radioisotopes are harmful. T or F
False. The decay of the isotopes cause harms not the radioisotope itself. When the machine beeps, it measures the decay of the isotope.
Give examples of natural background radiation
Thorium and Uranium are present in rocks and minerals
Th decay to 208 Pb
Ur decay to 206 Pb
Potassium -40 decay to Ca-40
present in traces for every natural potassium
Cosmic radition
-through interaction of cosmic rays with gases in the atmosphere
Why is radon harmful?
It is a gas and hence, it can leave the rock, leaving us exposed to breathing it in
Rank the types of radioactive decay from least ionizing to most ionizing
Gamma
Beta
Alpha decay
Rank the types of radioactive decay from least penetrating to most penetrating
Alpha decay
Beta
Gamma
What is the unit for activity?
Bequerel (Bq) = 1 nuclear disintegration per second
What is the unit for Absorbed dose?
Gray (Gy) = 1 J of absorbed energy per kg tissue (SI-Unit)
1 Gy = 100 rad
What is the unit for effective dose?
Sievert (Sv)
Define effective dose
multiplication of Absorbed dose with radiation weighting factor (Wr) (considers tissue and type of radiation)
Match these three unit symbols to its definition:
Sv, Bq, Gy
Sievert -effective dose
Bequerel - activity
Gray - absorbed dose
How much radiation can u get from
1) chest x-ray
2) average effective dose from natural bg radiation
3) one set of panoramic dental radiograph
4) single full body CT scan
5) hourly effective dose in direct vicinity to CHernobyl core and Fukushima directly after the accident?
0.07 mSv
2.4
5-10
10 to 30
300 and 1000
What is the average effective dose obtained from natural background radiation?
2.4 mSv
Who were the founding fathers of Nuclear fission?
Otto Hahn, Lise Mietner, Fritz Strassmann
Comparee Nuclear fission and nuclear fusion
Nuclear fission is the splitting of a nucleus into smaller nuclei which are radioactive
2 or more neutrons may be releaased as well. Some energy may also be released
The released neutrons may hit other uranium nuclei and cause them to split.
Even more neutrons are released which in turn can split more nuclei. This is called a chain reaction
Nuclear fission involves two atomic nuclei joining to form a large nucleus
Energy is released when this happens
The Sun and the stars use nuclear fusion to release energy
What is the working principle of gas-filled detectors?
filled the container with gas
ionize the gas along radiation path
accelerate primary ions by voltage and produce avalanche of ions
what is the proportional counter for?
Used to control voltage so that current is proportional to the energy of incoming particles.
What is the Geiger-Muller counter for?
runs at higher voltage
each single partcile produces an avalanche
Limitations: cannot differentiate between decay types and particle energies
Advantage: significant detector deadtime but less suitable for high count rates.
How is analysis carried out and how do you determine the element’s specific activity?
sample is bombarded by high neutron influx
elements capture neutron and become radioactive
analysis by gamma-spec
element concentration
neutron capture
radiation time
half-life of radioisotope
What are the advantages of Neutron activation analysis?
multiple-element for bulk analysis
minimum sample prep
analytical precision 1-5%
What is the working principle of X-ray fluorescence?
x-ray kicks out an inner electron
electron from an outer shell fills in the gap
emission of discrete energy
