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Nuclear fission
Nuclear fission: the fragmentation of large nuclei into smaller nuclei. It is a viable source of energy although the resulting radioactive waste is hazardous to life
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Nuclear fusion
The merging of small nuclei into larger ones. It is technologically and financially challenging to develop
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Some nuclear radiation consist of rapidly moving particles, such as ______ and _______, while others consist of rapidly moving _______, particles with a mass equal to that of one of the subatomic particles, but with the ________ ______.
- protons and neutrons
- antiparticles
- opposite charge
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Give an example of anitparticles
The positron, it has the same mass as an electron but it has a positive charge. It is denoted β+
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When an antiparticle encounters its corresponding particle, both particles are ________ and completely converted into ______.
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In electron capture, an electron in an atomic orbital is captured by the ______ and a ______ is converted into a _______.
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The most common types of radiation emitted by radioactive nuclei are _______, positively charged particles, _______, fast electrons ejected from the nucleus and _______, high frequency electromagnetic radiation.
- α particles
- β particles
- γ radiation
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Radioactivity is produced by _____ _____, a partial break up of the nucleus. This particular change in composition is called a ______ reaction. Nuclei that change their ________ spontaneously and emit ________ are called radioactive.
- nuclear decay
- nuclear reaction
- structure
- radiation
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Three differences between nuclear reactions and chemical reactions
- Different isotopes of the same element undergo essentially the same chemical reactions but their nuclei undergo very different nuclear reactions
- Some nuclear reactions, such as those in which the α or β particles are emitted from the nucleus, leave behind a nucleus with a different number of protons (result is daughter nuclei).
- Energy changes are very much greater for nuclear reactions than for chemical reactions
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To predict the identity of a daughter nucleus, note how the _____ and _____ numbers change when the parent nucleus ejects a particle. For example the radium-226 nucleus, with Z = 88, undergoes α decay, it emits an α particle with nuclear charge of +2 and a mass number of 4. What should the new daughter nucleus be and why?
- atomic and mass numbers
- Radon-222 with atomic number 86, because both total mass number and total nuclear charge are conserved in a nuclear reaction
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State the type of nuclear radiation and the symbol (including mass number and charge)
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The pattern of nuclear stability can be used to predict the likely mode of radioactive decay: neutron-rich nuclei tend to be _____ the band of stability and reduce their _______ count; while proton-rich nuclei tend to be _____ the band of stability and reduce their ______ count. In general, only ______ nuclides emit α particles
- above
- neutron
- below
- proton
- heavy
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The process of forming elements is _______, it occurs naturally. _______ & _______ were produced in the Big Bang; all other naturally occurring elements are descended from these two. As a result, nuclear reactions either take place in _____ or in _____.
- nucleosynthesis
- Hydrogen & helium
- stars
- space
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In order to make elements artificially, we need to simulate the conditions found inside a ____.
star
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The absorbed dose of radiation is the energy deposited in a sample (human body) when it is exposed to ________. The SI unit for absorbed dose is the ____ (__), which corresponds to an energy deposit of _____.
- radiation
- gray (Gy)
- 1 J*kg-1
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The original unit used for reporting dose was the ______ ______ dose (rad), the amount of radiation that deposits 10-2J of energy per kilogram of tissue, and so 1 rad = ____
- radiation absorbed dose
- 10-2 Gy
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The extent of radiation damage to living tissue depends on the type of ______ and the type of ______. We must therefore include the _______ ______ ______, Q, when assessing the damage that a given dose of each type of _______ may cause.
- radiation
- tissue
- relative biological effectiveness
- radiation
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For ___ and ___ radiation, Q is set arbitrarily around 1; however, for ___ radiation, Q is close to ____.
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The dose equivalent is the actual dose modified to take into account different destructive powers of various types of _______ & _____. State the formula
- radiations & tissue
- Dose equivalent (Sv) = Q * absorbed dose (Gy)
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Gieger counters make use of the ________ of a gas, usually _____, when it is exposed to nuclear radiation, and scintillation counters measure radiation by counting the flashes of light that are generated when ______ strikes a substance called _______.
- ionization
- argon
- radiation
- phosphor
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The _____ of a sample is the number of nuclear disintegration in a given time interval divided by the length of the interval.
activity
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The SI unit of activity is the ______ (__): one of which is equal to one nuclear disintegration per second. Another commonly used (non SI) unit of radioactivity is the ______(__). It is equal to 3.17 * 1010 nuclear disintegrations per second, the radioactive output of 1g of radium-226.
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As in a unimolecular chemical reaction, the rate law for nuclear decay is _____ order. That is, the relation between the rate of decay and the number N of radioactive nuclei present is given by the law of radioactive decay: (state the formula)
First order
Activity = rate of decay = k * N (k is the decay constant)
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A first order rate implies an ________ decay. It follows that the number N of nuclei remaining after a time (t) is given which formula?
exponential decay
N = N0e-kt (N0 is the number of radioactive nuclei present initially at t=0)
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If the total mass of an isotope in a sample is proportional to the number of nuclei of that isotope (that the sample contains), the _____ dependence of the mass of a radioactive isotope follows the same radioactiv decay law as the number of ______ in a sample. So m ~ N. What is the resulting equation?
m = m 0e -kt (where m 0 is the initial mass and m is the total mass of the radioactive isotope at time (t)
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Radioactive decay is normally discussed in terms of the half-life t1/2, the time needed for half the initial number of nuclei to disintegrate. t1/2 can be related to k by setting N = 1/2N0 and t = t1/2. What is the resulting equation?
t1/2 = ln2/k
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In isotopic dating, we measure the activity of the radioactive isotopes that they (old artifacts) contain. The more important form is _______ dating, which uses _____ decay of carbon-14, for which the half-life is 5730a.
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When an organism dies, it no longer exchanges _______ with its surrounding. However, ________ nuclei already inside the organism continue to decay with a constant ____ ____, and so the ratio of _______ to _______ decreases
- carbon
- carbon-14
- half life
- carbon-14 to carbon-12
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