Chapter 25
5730
carbon-14 has a half life of ____ years
alpha radiation
consists of helium nuclei that have been emitted from a radioactive source (2 protons and 2 neutrons has a double positive charge)
ions, plate
devices to detect radiation operate because of the effects of the radiation when it strikes atoms or molecules for example the radiation can produce ____ which can be detected or it can expose a photographic _____ and produce images that show where the plate has been exposed to radiation
positron emission
during ________ ________, a proton changes to a neutron; when electron and positron collide, masses convert to energy in gamma rays; known as antimatter
curium
element named for marie and pierre curie
polonium
element named for polish scientist marie curie
radium
element which has invisible rays put out
1
for elements of low atomic number (below about 20), the ratio of neutrons to protons is about _
antoine henri becquerel
french chemist who accidentally discovered uranium
waste
fuel rods from nuclear power plants are one major source of nuclear _____
high
fusion reactions only occur at very ____ temperatures (in excess of 40,000,000°C
more
fusion reactions, in which small nuclei combine, release much ____ energy than fission reactions in which large nuclei split
uranium-238
has a long half life of 4.5 billion years; decays through complex series of radioisotopes to the stable isotope lead-206
repel
if a force did not hold these subatomic particles together, the like charged protons would ____ one another and fly apart
energy
if all the masses in a nuclear reaction were measured accurately enough, you would find that mass is not conserved because an extremely small quantity of mass is converted to ______ released in radioactive decay
solar fusion
in _____ ______, hydrogen nuclei (protons) fuse to make helium nuclei
react
in a chain reaction, some of the neutrons produced _____ with other fissionable atoms, producing more neutrons which react with still more fissionable atoms
uncontrolled
in an ____________ nuclear chain reaction, the total energy release takes only fractions of a second (atomic bombs start these)
electrons
in chemical reactions, atoms tend to attain stable electron configurations by losing or sharing _________
changes
in nuclear reations, the nuclei of unstable isotopes, called radioisotopes, gain stability by undergoing _______ which are always accompanied by the emission of large amounts of energy
neutron
james chadwick's discovery of the ______ involved a transmutation when neutrons were produced when beryllium-9 was bombarded with alpha particles
uranium ore
large deposits of _______ ___ make it less expensive to mine new fuel than to reprocess depleted fuel
medicine
many artificially produced radioisotopes have short half lives which is useful in nuclear ________
nature
many transmutations can occur in ______ such as the production of carbon-14 from naturally occurring nitrogen-14 and the process of naturally occurring uranium-238 to a stable isotope (bombarded by neutrons)
cadmium
material of control rods in neutron absorption
carbon-13, carbon-12
most of earth's carbon consists of more stable isotopes ______-__ and ______-__
controlled
nuclear reactors use _________ fission to produce useful energy by generating energy in the form of heat then using a coolant (liquid sodium or water) to remove heat to generate steam which drives a turbine to generate electricity; involves neutron moderation and neutron absorption
beta radiation
occurs when an electron from a broken apart neutron is emitted and the neutron forms a proton which stays in the nucleus
264
out of more than 1500 different known nuclei, only ___ are stable (not radioactive) and do not decay or change with time
ernest rutherford
performed the first artificial mutation by bombarding nitrogen gas with alpha particles to produce an unstable isotope of fluorine which quickly decomposes to a stable isotope of oxygen and a proton
marie curie
polish scientist whose research led to many discoveries about radiation and radioactive elements; she and her husband won the nobel peace prize for work on radioactivity in physics and for research on radioactive elements in chemistry; died from leukemia caused by long term exposure to radiation
cannot
radiation ______ be seen, heard, felt, or smelled and radiation detection instruments must be used to alert people to the presence of radiation and to monitor its level
ionizing radiation
radiation with enough energy to knock electrons off some atoms of a bombarded substance to produce ions; radiation emitted by radioisotopes
spontaneous
radioactive decay is ___________ and does not require any input of energy
technetium-99m
radioisotope used to detect brain tumors and liver disorders
phosphorus-32
radioisotope used to detect skin cancer
iodine-131
radioisotope used to detect thyroid problems because the thyroid gland extracts iodide ions from the bloodstream and uses them to make the hormone thyroxine
medical, diseases
radioisotopes can be used to diagnose _______ problems and, in some cases, to treat ________
tracers
radioisotopes used in agriculture to test the effects of herbicides, pesticides, and fertilizers; injected into substance being tested to make it radioactive the plants are treated with radioactively labeled substance then radioactivity of plants is measured to find locations of substance
proton
rutherford's experiment eventually led to the discovery of the ______
carbon-14
scientists often find the age of an object that was once part of a living system by measuring the amount of ______-__ it contains
artifacts
scientists use the half lives of some radioisotopes found in nature to determine the age of ancient _________
sun
the ___ is directly and indirectly the source of most energy used on earth; its released energy results from nuclear fusion
neutron-proton
the _______-______ ratio determines the type of decay that occurs
transmutation
the conversion of an atom of one element to an atom of another element
rays
the curies discovered that the ____ emitted by the uranium atoms caused the fogging of plates
dalton's
the discovery of radioactivity disproved _______ assumption that atoms are indivisible because a radioisotope undergoes drastic changes as it emits radiation
fission bomb
the high temperatures required for fusion have been achieved by using a _______ ____, a triggering device for setting off a hydrogen bomb which is an uncontrolled fusion device and is a process of no use as a controlled generator of power
band of stability
the location of stable nuclei on a neutron vs. proton plot
small
the mass of an electron is extremely _____ when compared to a proton
uranium-235, plutonium-239
the only two fissionable isotopes
radiation
the penetrating rays and particles emitted by a radioactive source
radioactivity
the process by which nuclei emit particles and rays
fusion
the process of combining nuclei to produce a nucleus of greater mass
constant
the ratio of carbon-14 to other carbon isotopes remains fairly ________ due to high energy cosmic rays from space which produce carbon-14 in the upper atmosphere and plants which use carbon dioxide in the atmosphere
fission
the splitting of a nucleus into smaller fragments, accompanied by the release of neutrons and a large amount of energy
ratio, size
the stability of a nucleus depends on the _____ of neutrons to protons in the nucleus and the overall ____ of the nucleus; too many or two few neutrons relative to the number of protons makes a nucleus unstable
half life
the time required for one-half of the nuclei of a radioisotope sample to decay to products; can be as short as a fraction of a second or as long as billions of years
appealing
the use of controlled nuclear fusion as an energy source on earth is _________ because potential fuels are inexpensive and readily available
assembly, reactor core
three hundred fuel rods bundled together form an ________, and one hundred assemblies form the _______ ____
alpha, beta, gamma
three main types of nuclear radiation
radioactive decay, bombard
transmutation can occur by ___________ _____ or when particles (protons, neutrons, or electrons) _______ the nucleus of an atom
artificial transmutation
transmutation done in laboratories or nuclear reactions
water, carbon (graphite)
two good neutron moderators
counts/min x g C
unit for expressing decay rate
unaffected
unlike chemical reactions, nuclear reactions are __________ by changes in temperature, pressure, the presence of catalysts, and the compounds in which the unstable isotopes are present (cannot be sped up, slowed down, or turned off)
different
unstable radioisotopes of one element are transformed into stable (nonradioactive) isotopes of a _________ element
neptunium, plutonium
uranium-238 is bombarded with slow neutrons from a nuclear reactor and some nuclei capture neutrons to produce uranium-239 which is radioactive and emits a beta particle and a product of isotope of artificial radioactive element __________ which is unstable and decays emitting a beta particle to produce a second artificial element, _________
electron capture
when nuclei have too few neutrons relative to the number of protons, these nuclei increase their stability by converting a proton to a neutron and an electron is captured during this process
beta emission
when nuclei have too many neutrons relative to protons, these nuclei decay by turning a neutron into a proton to emit a beta particle from the nucleus (increases the number of protons while decreasing the number of neutrons)
radon gas
_____ ___ can accumulate indoors and pose a health risk
alpha emission
_____ ________ increases the neutron-proton ration, which tends to increase the stability of the nucleus
storage racks
_______ _____ at the bottom of pools are designed to hold the spent fuel assemblies but the rods continue to produce heat for years after their removal from the core
less, more
a beta particle has ____ charge and mass than an alpha particle therefore it is ____ penetrating; can pass through paper but are stopped by aluminum foil or thin pieces of wood
americium
a common household smoke detector uses the radiation from a radioisotope ________
geiger counter
a device that uses a gas-filled metal tube to detect radiation; when ionizing radiation penetrates the tube, the gas becomes an electrical conductor so current can flow and trigger audible clicks from a built in speaker; can detect alpha, beta, and gamma radiation
scintillation counter
a device that uses a phosphor-coated surface to detect radiation; strikes of ionizing radiation produce bright flashes of light (scintillations) which are converted into electronic pulses to be measured and recorded; detect all types of radiation
cancer
a disease in which abnormal cells in the body are produced at a rate far beyond the rate for normal cells
gamma ray (γ)
a high energy photon emitted by a radioisotope; are electromagnetic radiation; often emitted with alpha or beta particles during radioactive decay
positron
a particle with the mass of an electron but a positive charge
alpha particle (α)
a positively charged particle emitted from certain radioactive nuclei; it consists of two protons and two neutrons and is identical to the nucleus of a helium atom
neutron activation analysis
a procedure used to detect trace amounts of elements in samples by bombarding the sample with neutrons from a radioactive source; some atoms become radioactive and their half life and type are detected to determine what types of radioisotopes were produced and what element was originally in the sample; used to detect art forgeries and gun powder residue
neutron absorption
a process that decreases the number of slow-moving neutrons in a nuclear reactor; accomplished by using control rods made of cadmium which absorbs neutrons
neutron moderation
a process used in nuclear reactors to slow down neutrons so the reactor fuel captures them to continue the chain reaction; necessary because neutrons move so fast that they would pass through a nucleus without being absorbed
film badge
a radiation detection device that consists of several layers of photographic film covered with black lightproof paper, all encased in a plastic or metal holder; worn by people who work near radiation; strength and type of radiation are determined by darkening of film; do not protect from radiation - only measure the degree of exposure to it
radon-222
a radioactive isotope that is present naturally in the soil in some areas and has a constant rate of decay
20
above atomic number __, stable nuclei have more neutrons than protons
new
after each half life, half of the existing radioactive atoms have decayed into atoms of a ___ element
holding tanks
all nuclear power plants have _______ _____, or swimming pools (usually 12 meters deep), for spent fuel rods where water acts cools them and acts as a radiation shield to reduce the radiation levels
83
all nuclei that have an atomic number greater than __ are radioactive and have too many protons and neutrons to be stable and therefore undergo radioactive decay - most emit alpha particles
hydrogen
all nuclei, except those in ________ atoms, consist of neutrons and two or more protons
nuclear force
an attractive force that acts between all nuclear particles that are extremely close together, such as protons and neutrons in a nucleus; dominates over electromagnetic repulsions and holds nucleus together
beta particle (β)
an electron resulting from the breaking apart of neutrons in an atom
radioisotope
an isotope that has an unstable nucleus and undergoes radioactive decay
estimate
an organism stops exchanging carbon within the environment when it dies and its carbon-14 atoms decay without being replaced which therefore allows the ratio of carbon-14 to stable carbon to enable archaeologists to ________ its age
radioactive decay
an unstable nucleus releases energy by emitting radiation during the process of ___________ ______
transuranium element
any element in the periodic table with atomic number above 92, the atomic number of uranium; all undergo transmutation; none occur in nature; all are radioactive; synthesized in nuclear reactors (produce beams of low energy particles) and nuclear accelerators (accelerate bombarding particles to very high speeds)
off site
at some nuclear plants, there is no space left in the storage pool so in order to keep these plants open, their fuel rods must be moved to ___ ____ storage facilities
no, extremely
because gamma rays have __ mass or charge, the emission of gamma radiation does not alter the atomic number or mass of an atom and are _________ penetrating and very dangerous to the human body - can be stopped (although not completely) by several meters of concrete or several centimeters of lead
not
because of their large mass and charge, alpha particles do not tend to travel very far and are ___ very penetrating; a sheet of paper or skin easily stops them but they are dangerous when ingested because they do not have to travel far to penetrate soft tissue and cause damage
