Chapter 31: Radioactivity and Nuclear Physics

activity

the rate of decay for radioactive nuclides

alpha decay

type of radioactive decay in which an atomic nucleus emits an alpha particle

alpha rays

one of the types of rays emitted from the nucleus of an atom

antielectron

another term for positron

antimatter

composed of antiparticles

atomic mass

the total mass of the protons, neutrons, and electrons in a single atom

atomic number

number of protons in a nucleus

barrier penetration

quantum mechanical effect whereby a particle has a nonzero probability to cross through a potential energy barrier despite not having sufficient energy to pass over the barrier; also called quantum mechanical tunneling

becquerel

SI unit for rate of decay of a radioactive material

beta decay

type of radioactive decay in which an atomic nucleus emits a beta particle

beta rays

one of the types of rays emitted from the nucleus of an atom

binding energy

the energy needed to separate nucleus into individual protons and neutrons

binding energy per nucleon

the binding energy calculated per nucleon; it reveals the details of the nuclear force—larger the BE/𝐴, the more stable the nucleus

carbon-14 dating

a radioactive dating technique based on the radioactivity of carbon-14

chart of the nuclides

a table comprising stable and unstable nuclei

curie

the activity of 1g of 226⁢Ra, equal to 3.70×1010⁢Bq

daughter

the nucleus obtained when parent nucleus decays and produces another nucleus following the rules and the conservation laws

decay

the process by which an atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles

decay constant

quantity that is inversely proportional to the half-life and that is used in equation for number of nuclei as a function of time

decay equation

the equation to find out how much of a radioactive material is left after a given period of time

decay series

process whereby subsequent nuclides decay until a stable nuclide is produced

electron capture

the process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino

electron capture equation

equation representing the electron capture

electron’s antineutrino

antiparticle of electron’s neutrino

electron’s neutrino

a subatomic elementary particle which has no net electric charge

gamma decay

type of radioactive decay in which an atomic nucleus emits a gamma particle

gamma rays

one of the types of rays emitted from the nucleus of an atom

Geiger tube

a very common radiation detector that usually gives an audio output

half-life

the time in which there is a 50% chance that a nucleus will decay

ionizing radiation

radiation (whether nuclear in origin or not) that produces ionization whether nuclear in origin or not

isotopes

nuclei having the same 𝑍 and different 𝑁s

magic numbers

a number that indicates a shell structure for the nucleus in which closed shells are more stable

mass number

number of nucleons in a nucleus

neutrino

an electrically neutral, weakly interacting elementary subatomic particle

neutron

a neutral particle that is found in a nucleus

nuclear radiation

rays that originate in the nuclei of atoms, the first examples of which were discovered by Becquerel

nuclear reaction energy

the energy created in a nuclear reaction

nucleons

the particles found inside nuclei

nucleus

a region consisting of protons and neutrons at the center of an atom

nuclide

a type of atom whose nucleus has specific numbers of protons and neutrons

parent

the original state of nucleus before decay

photomultiplier

a device that converts light into electrical signals

positron

the particle that results from positive beta decay; also known as an antielectron

positron decay

type of beta decay in which a proton is converted to a neutron, releasing a positron and a neutrino

protons

the positively charged nucleons found in a nucleus

quantum mechanical tunneling

quantum mechanical effect whereby a particle has a nonzero probability to cross through a potential energy barrier despite not having sufficient energy to pass over the barrier; also called barrier penetration

radiation detector

a device that is used to detect and track the radiation from a radioactive reaction

radioactive

a substance or object that emits nuclear radiation

radioactive dating

an application of radioactive decay in which the age of a material is determined by the amount of radioactivity of a particular type that occurs

radioactivity

the emission of rays from the nuclei of atoms

radius of a nucleus

the radius of a nucleus is 𝑟=𝑟0⁢𝐴1/3

range of radiation

the distance that the radiation can travel through a material

rate of decay

the number of radioactive events per unit time

scintillators

a radiation detection method that records light produced when radiation interacts with materials

solid-state radiation detectors

semiconductors fabricated to directly convert incident radiation into electrical current

tunneling

a quantum mechanical process of potential energy barrier penetration

A mass unit convenient to atomic and nuclear processes is the unified atomic mass unit (u), defined to be

1/12 of the mass of a carbon-12 atom.

alpha nuclear decay equation

The equation representing the process in which an alpha particle is emitted from a nucleus, typically written as A\rightarrow A-4+X.

Nuclear decay releases an amount of energy 𝐸 related to the mass destroyed Δ⁢𝑚 by

the equation E=Δ⁢𝑚c², where c is the speed of light.

Beta decay equations

describe the transformation of a neutron into a proton and an electron, emitting a beta particle in the process.

𝛾 decay equation

describes the process of gamma radiation emission from an excited nucleus, which transitions to a lower energy state without a change in the number of protons or neutrons.

The activity 𝑅 of a source is related to 𝑁 and 𝑡1/2 by

the equation R = λN, where λ is the decay constant.

Since 𝑁 has an exponential behavior as in the equation 𝑁=𝑁0⁢𝑒−𝜆𝑡, the activity also has an exponential behavior, given by