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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
The merging of small nuclei into larger ones. It is technologically and financially challenging to develop
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
- opposite charge
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+
When an antiparticle encounters its corresponding particle, both particles are ________ and completely converted into ______.
In electron capture, an electron in an atomic orbital is captured by the ______ and a ______ is converted into a _______.
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
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
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
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
State the type of nuclear radiation and the symbol (including mass number and charge)
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
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 _____.
- Hydrogen & helium
In order to make elements artificially, we need to simulate the conditions found inside a ____.
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 _____.
- gray (Gy)
- 1 J*kg-1
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
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.
- relative biological effectiveness
For ___ and ___ radiation, Q is set arbitrarily around 1; however, for ___ radiation, Q is close to ____.
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)
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 _______.
The _____ of a sample is the number of nuclear disintegration in a given time interval divided by the length of the interval.
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.
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)
Activity = rate of decay = k * N (k is the decay constant)
A first order rate implies an ________ decay. It follows that the number N of nuclei remaining after a time (t) is given which formula?
N = N0e-kt (N0 is the number of radioactive nuclei present initially at t=0)
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 = m0
is the initial mass and m is the total mass of the radioactive isotope at time (t)
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
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.
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
- half life
- carbon-14 to carbon-12