Chemistry

# Key Terms

ChemistryKey Terms
alpha (α) decay
loss of an alpha particle during radioactive decay
alpha particle
or $24He24He$ or $24α)24α)$ high-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons
antimatter
particles with the same mass but opposite properties (such as charge) of ordinary particles
band of stability
(also, belt of stability, zone of stability, or valley of stability) region of graph of number of protons versus number of neutrons containing stable (nonradioactive) nuclides
becquerel (Bq)
SI unit for rate of radioactive decay; 1 Bq = 1 disintegration/s
beta (β) decay
breakdown of a neutron into a proton, which remains in the nucleus, and an electron, which is emitted as a beta particle
beta particle
$(β(β$ or $−10e−10e$ or $−10β)−10β)$ high-energy electron
binding energy per nucleon
total binding energy for the nucleus divided by the number of nucleons in the nucleus
chain reaction
repeated fission caused when the neutrons released in fission bombard other atoms
chemotherapy
similar to internal radiation therapy, but chemical rather than radioactive substances are introduced into the body to kill cancer cells
containment system
(also, shield) a three-part structure of materials that protects the exterior of a nuclear fission reactor and operating personnel from the high temperatures, pressures, and radiation levels inside the reactor
control rod
material inserted into the fuel assembly that absorbs neutrons and can be raised or lowered to adjust the rate of a fission reaction
critical mass
amount of fissionable material that will support a self-sustaining (nuclear fission) chain reaction
curie (Ci)
larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 $××$ 1010 disintegrations/s
daughter nuclide
nuclide produced by the radioactive decay of another nuclide; may be stable or may decay further
electron capture
combination of a core electron with a proton to yield a neutron within the nucleus
electron volt (eV)
measurement unit of nuclear binding energies, with 1 eV equaling the amount energy due to the moving an electron across an electric potential difference of 1 volt
radiation delivered by a machine outside the body
fissile (or fissionable)
when a material is capable of sustaining a nuclear fission reaction
fission
splitting of a heavier nucleus into two or more lighter nuclei, usually accompanied by the conversion of mass into large amounts of energy
fusion
combination of very light nuclei into heavier nuclei, accompanied by the conversion of mass into large amounts of energy
fusion reactor
nuclear reactor in which fusion reactions of light nuclei are controlled
gamma (γ) emission
decay of an excited-state nuclide accompanied by emission of a gamma ray
gamma ray
or $00γ)00γ)$ short wavelength, high-energy electromagnetic radiation that exhibits wave-particle duality
Geiger counter
instrument that detects and measures radiation via the ionization produced in a Geiger-Müller tube
gray (Gy)
SI unit for measuring radiation dose; 1 Gy = 1 J absorbed/kg tissue
half-life (t1/2)
time required for half of the atoms in a radioactive sample to decay
(also, brachytherapy) radiation from a radioactive substance introduced into the body to kill cancer cells
radiation that can cause a molecule to lose an electron and form an ion
magic number
nuclei with specific numbers of nucleons that are within the band of stability
mass defect
difference between the mass of an atom and the summed mass of its constituent subatomic particles (or the mass “lost” when nucleons are brought together to form a nucleus)
mass-energy equivalence equation
Albert Einstein’s relationship showing that mass and energy are equivalent
millicurie (mCi)
larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 $××$ 1010 disintegrations/s
radiation that speeds up the movement of atoms and molecules; it is equivalent to heating a sample, but is not energetic enough to cause the ionization of molecules
nuclear binding energy
energy lost when an atom’s nucleons are bound together (or the energy needed to break a nucleus into its constituent protons and neutrons)
nuclear chemistry
study of the structure of atomic nuclei and processes that change nuclear structure
nuclear fuel
fissionable isotope present in sufficient quantities to provide a self-sustaining chain reaction in a nuclear reactor
nuclear moderator
substance that slows neutrons to a speed low enough to cause fission
nuclear reaction
change to a nucleus resulting in changes in the atomic number, mass number, or energy state
nuclear reactor
environment that produces energy via nuclear fission in which the chain reaction is controlled and sustained without explosion
nuclear transmutation
conversion of one nuclide into another nuclide
nucleon
collective term for protons and neutrons in a nucleus
nuclide
nucleus of a particular isotope
parent nuclide
unstable nuclide that changes spontaneously into another (daughter) nuclide
particle accelerator
device that uses electric and magnetic fields to increase the kinetic energy of nuclei used in transmutation reactions
positron $(+10β(+10β$ or $+10e)+10e)$
antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge
positron emission
(also, β+ decay) conversion of a proton into a neutron, which remains in the nucleus, and a positron, which is emitted
SI unit for measuring radiation dose, frequently used in medical applications; 1 rad = 0.01 Gy
device that measures ionizing radiation and is used to determine personal radiation exposure
use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing
spontaneous decay of an unstable nuclide into another nuclide
chains of successive disintegrations (radioactive decays) that ultimately lead to a stable end-product
phenomenon exhibited by an unstable nucleon that spontaneously undergoes change into a nucleon that is more stable; an unstable nucleon is said to be radioactive
highly accurate means of dating objects 30,000–50,000 years old that were derived from once-living matter; achieved by calculating the ratio of $614C : 612C 614C : 612C$ in the object vs. the ratio of $614C : 612C 614C : 612C$ in the present-day atmosphere
isotope that is unstable and undergoes conversion into a different, more stable isotope
use of radioisotopes and their properties to date the formation of objects such as archeological artifacts, formerly living organisms, or geological formations
reactor coolant
assembly used to carry the heat produced by fission in a reactor to an external boiler and turbine where it is transformed into electricity
relative biological effectiveness (RBE)
measure of the relative damage done by radiation
roentgen equivalent man (rem)
unit for radiation damage, frequently used in medicine; 100 rem = 1 Sv
scintillation counter
instrument that uses a scintillator—a material that emits light when excited by ionizing radiation—to detect and measure radiation
sievert (Sv)
SI unit measuring tissue damage caused by radiation; takes into account energy and biological effects of radiation
strong nuclear force
force of attraction between nucleons that holds a nucleus together
subcritical mass
amount of fissionable material that cannot sustain a chain reaction; less than a critical mass
supercritical mass
amount of material in which there is an increasing rate of fission
transmutation reaction
bombardment of one type of nuclei with other nuclei or neutrons
transuranium element
element with an atomic number greater than 92; these elements do not occur in nature
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