Chapter 11: Nuclear Reactions

radioactivity

spontaneous emission of particles or energy from an atomic nucleus as it disintegrates

alpha particle

the nucleus of a helium atom (two protons and two neutrons) emitted as radiation from a decaying heavy nucleus; also known as an alpha ray

beta particle

high-energy electron emitted as ionizing radiation from a decaying nucleus; also known as a beta ray

gamma ray

very short wavelength electromagnetic radiation emitted by decaying nuclei

beta particle

A high-speed electron ejected from a nucleus during radioactive decay is called a(n)

radioactive decay

the natural spontaneous disintegration or decomposition of a nucleus

nucleons

name used to refer to both the protons and neutrons in the nucleus of an atom

a decrease in the atomic number by two

The ejection of an alpha particle from a nucleus results in

polonium

An atom of radon-222 loses an alpha particle to become a more stable atom of

nuclear force

a strong fundamental force of attraction that is functional only at extremely short distances

electromagnetic force

the force of repulsion between like charges, is the operational force

stable

does not undergo radioactive decay

band of stability

a region of a graph of the number of neutrons versus the number of protons in nuclei; nuclei that have the neutron to proton ratios located in this band do not undergo radioactive decay

alpha particle

An atom of an isotope with an atomic number greater than 83 will probably emit

beta particle

An atom of an isotope with a large neutron-to-proton ratio will probably emit a(n)

excited state

sometimes leaves the nucleus with an excess of energy

alpha particle

A sheet of paper will stop a(n)

gamma ray

The most penetrating of the three common types of nuclear radiation is the

size of the sample

The rate of radioactive decay can be increased by increasing the

half-life

the time required for one-half of the unstable nuclei in a radioactive substance to decay into a new element

isotope A

Isotope A has a half-life of seconds, and isotope B has a half-life of millions of years. Which isotope is more radioactive?

ionization counter

one type that measures ions produced by radiation

scintillation counter

measures the flashes of light produced when radiation strikes a phosphor

Phosphor

substances that emit a flash of light when excited by radiation

activity

a measure of the number of nuclear disintegrations per unit of time

curie

unit of nuclear activity defined as 3.70×10¹⁰ nuclear disintegrations per second

becquerel

defined as one nuclear disintegration per second

rem

measure of radiation that considers the biological effects of different kinds of ionizing radiation

rad

a measure of radiation received by a material (radiation absorbed dose)

background radiation

ionizing radiation (alpha, beta, gamma, etc.) from natural sources; between 100 and 500 millirems/yr of exposure to natural radioactivity from the environment

linear model

proposes that any radiation exposure above zero is damaging and can produce cancer genetic damage.

Threshold model

proposes that the human body can repair damage and get rid of damaging free polyatomic ions up to a certain exposure level

curie

A measure of radioactivity at the source is the

rem

A measure of radiation received that considers the biological effect resulting from the radiation is the

mass defect

the difference between the sum of the masses of the individual nucleons forming a nucleus and the actual mass of that nucleus

binding energy

the energy required to break a nucleus into its constituent protons and neutrons; also the energy equivalent released when a nucleus is formed

nuclear fission

nuclear reaction of splitting a massive nucleus into more stable, less massive nuclei with an accompanying release of energy

nuclear fusion

nuclear reaction of low-mass nuclei fusing together to form more stable and more massive nuclei with an accompanying release of energy

chain reaction

a self-sustaining reaction where some of the products are able to produce more reactions of the same kind; in a nuclear chain reaction, neutrons are the products that produce more nuclear reactions in a self-sustaining series

critical mass

mass of fissionable material needed to sustain a chain reaction

nuclear reactor

a steel vessel in which a controlled chain reaction of fissionable material releases energy

fuel rod

a long zirconium alloy tube

controls rods

constructed of materials, such as cadmium, that absorb neutrons

Primary loop

the energy released is carried away from the reactor by pressurized water in a closed pipe

96% usable uranium and plutonium

Used fuel rods from a nuclear reactor contain about

false

An alpha particle is really a high-energy electron ejected from a uranium atom’s nucleus.

false

When

 undergoes beta-decay, the product is

.

true

Isotopes with an even number of both protons and neutrons are generally stable.

true

A radioactive decay reaction produces a simpler, more stable nucleus

false

If element X undergoes radioactive decay to element Y with a half-life of five minutes, then, after 10 minutes, the sample of X has completely changed into element Y.

false

Alpha radiation is the least dangerous as alpha particles can be stopped by your skin.

true

The threshold model of radiation poisoning proposes that under a certain level, your body can repair the damage produced by radiation.

false

The mass of a nucleus is slightly greater than the sum of the masses of its individual protons and neutrons.

true

Nuclear power reactors cannot explode like an atom bomb because there is not enough of the fissionable U-235 in a reactor to maintain a chain reaction.

true

Airline crews receive roughly three times the background radiation of those of us who spend most of our time on the ground.

All of the choices are correct.

Which type(s) of radiation ionizes atoms and molecules.

density of nearby electrons.

The decay rate of a Uranium-235 can be increased by increasing the

0.150 rem

The amount of radiation we are naturally exposed to during a year is nearly

Pu-239

Besides Uranium-235, another isotope that can undergo nuclear fission is

nuclear force

The two positively charged protons in a Helium-4 nucleus stay close together due to the

1/16

The radioactive isotope Z has a half-life of 12 hours. After 2 days, the fraction of the original amount remaining is

and the mass number remain the same

When an isotope releases gamma radiation the atomic number