10: Radioactivity and Nuclear Processes

Terms in this set (41)

radioactive nuclei
nuclei that undergo spontaneous changes and emit energy in the form of radiation.
radioactive decay
a process in which an unstable nucleus changes energy states and in the process emits radiation.
alpha particle
the particle that makes up alpha rays. it is identical to the helium nucleus and is composed of two protons and two neutrons.
beta particle
the particle that makes up beta rays. it is identical to an electron but is produced in the nucleus when a neutron is changed into a proton and an electron.
gamma ray
a high-energy ray that is like an X-ray, but with a higher energy.
radioisotope
an isotope of an element that emits nuclear radiation.
daughter nuclei
the new nuclei produced when unstable nuclei undergo radioactive decay.
positron
a positively charged electron
electron capture
a mode of decay for some unstable nuclei in which an electron from outside the nucleus is drawn into the nucleus, where it combines with a proton to form a neutron.
half-life
the time required for one-half the unstable nuclei in a sample to undergo radioactive decay.
radical or free radical
an electron-deficient particle that is very reactive.
acute radiation syndrome
the condition associated with and following short-term exposure to intense radiation.
inverse square law of radiation
a mathematical way of saying that the intensity to radiation is inversely proportional to the square of the distance from the source of the radiation.
physical unit of radiation
a radiation measurement unit indicating the activity of the source of the radiation; for example, the number of nuclear decay per minute.
biological unit of radiation
a radiation measurement unit indicating the damage caused by radiation in living tissue.
curie
a physical unit of radiation measurement corresponding to 3.7 X 10^10 nuclear disintegration per second.
becquerel
a physicalunit of radiation measurement corresponding to one nuclear disintegration per second.
roentgen
a biological unit of radiation measurement used with X-rays and gamma rays; the quantity of radiation taht generates 2.1 X 10^9 ion pairs per 1 cm^3 of dry air or 1.8 X 10^12 ion pairs per 1 g of tissue.
rad
a biological unit of radiation measurement corresponding to the transfer of 1 X 10^-3 cal of energy to 1 kg of tissue.
gray
a biological unit of radiation measurement corresponding to the transfer of 1 J of energy to 1 kg of tissue.
rem
a biological unit of radiation measurement corresponding to the health effect produced by 1 roentgen of gamma or X-rays regardless of the type of radiation involved.
scintillation counter
a radiation-detection device operating on the principle that phosphors give off light when struck by radiation.
Geiger-Muller tube
a radiation-detection device operating on the principle that ions form when radiation passes through a tube filled with low-pressure gas.
tracer
a radioisotope used medically because its progress through the body or localization in specific organs can be followed.
hot spot
tissue in which a radioactive tracer concentrates.
cold spot
tissue from which a radioactive tracer is excluded or rejected.
radioactive dating
a process for determining the age of artifacts and rocks, based on the amount of half-life of radioisotopes contained in the object.
moderators
materials capable of slowing down neutrons that pass through them.
cyclotron
a cyclic particle accelerator that works by changing electrical polarities as charged particles cross a gap. The particles are kept moving in a spiral path by a strong magnetic field.
linear accelerator
a particle accelerator that works by changing electrical polarities as charged particles cross gaps between segments of a long tube.
transuranium elements
synthetic elements with atomic numbers greater than that of uranium.
nuclear fission
a process in which large nuclei split into smaller, approximately equal-sized nuclei when bombarded by neutrons.
chain reaction
a nuclear reaction in which the products of one reaction cause a repeat of the reaction to take place. In the case of uranium fission, neutrons from fission reactions cause other fission reactions to occur.
expanding or branching chain reaction
a reaction in which the products of one reaction cause more than one more reaction to occur.
critical reaction
a constant-rate chain reaction.
supercritical reaction
a branching chain reaction.
critical mass
the minimum amount of fissionable material needed to sustain a critical chain reaction at a constant rate.
supercritical mass
the minimum amount of fissionable material that must be present to cause a branching chain reaction to occur.
breeder reaction
a nuclear reaction in which isotopes that will not undergo spontaneous fission are changed into isotopes that will.
thermonuclear reactions
nuclear fusion reactions that require a very high temperature to start.
nuclear fusion
a process in which small nuclei combine or fuse to form larger nuclei.
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