Chapter 33: Nuclear Physics

Atomic Number Z

The number of protons or electrons in an atom

Mass Number A

The number of protons plus neutrons in the nucleus

Neutron Number N

the number of neutrons in the nucleus. It is equal to the difference between the mass number and the atomic number

Isotope

An isotope of a chemical elements has the same number of protons as the element but a different number of neutrons. An isotope reacts chemically in the same way as the parent element. Its observable difference is its different atomic mass, which comes from the excess or deficiency of neutrons in the nucleus

Atomic mass

The mass of a chemical element that is listed in the periodic table of the elements. That atomic mass is an average of the masses of its different isotopes

Strong nuclear force

The force that binds protons and neutrons together in the nucleus. Whenever the nuclear force is less than the electrostatic force, the nucleus breaks up or decays, and emits radioactive particles

Mass defect

The difference in mass between the sum of the masses of the constituents of a nucleus and the mass of the nucleus

Binding energy

The energy that binds the nucleus together. It is the mass defect expressed as an energy

Radioactivity

The spontaneous disintegration of the nuclei of an atom with the emissions of alpha, beta, or gamma particles

Activity

The rate at which nuclei decay with time

Half-life

The time it takes for half the original radioactive nuclei to decay

Alpha decay

a disintegration of an atomic nucleus whereby an alpha particle is emitted. The original element of atomic number Z is transmuted into a new chemical element of atomic number Z-2

Beta Decay, -B

A nuclear decay whereby a neutron within the nucleus decays into a proton, an electron, and an antineutrino. The proton stays in the nucleus, but the electron and antineutrino are emitted. Thus, the atomic number Z increases by 1, but the mass number A stays the same. Hence, a chemical element Z is transmuted into the element Z+1

Beta Decay, B+

A nuclear decay whereby a proton within the nucleus decays into a proton, a positron and a neutrino. The positron and neutrino are emitted but the neutron stays behind in the nucleus The atomic number Z of the element decreases by one because of the loss of the proton. Hence, an element of atomic number Z is converted into the element Z-1

Q value of a nuclear reaction

The energy available in a reaction caused by the difference in mass between the reactants and the products

Exoergic reaction

A nuclear reaction in which energy is released. It is sometimes called an exothermic reaction

Endoergic reaction

A nuclear reaction in which energy must be added to the system to make the reaction proceed. It is sometimes called an endothermic reaction

Nuclear fission

The process of splitting a heavy atom into two lighter atoms

Nuclear fusion

The process in which lighter nuclei are joined together to produce a heavier nucleus with a large amount of energy released

Nucleosynthesis

The formation of the nuclei of all the chemical elements by the process of fusion within the stars

Radioactive dating

a technique in which the age of very old objects can be determined by the amount of unstable isotopes still contained in them

Representation of a nucleus

A visual depiction showing the arrangement of protons and neutrons within an atomic nucleus, often represented by a symbol that indicates the number of each type of particle.

Rate of nuclear decay

The speed at which unstable isotopes lose energy by emitting radiation, expressed as a half-life or decay constant.

Radioactive decay law

The principle that describes the statistical nature of radioactive decay, stating that the rate of decay of a radioactive substance is proportional to the amount of the substance remaining. It follows an exponential decay pattern.

Decay constant

A value that represents the probability of decay of a radioactive isotope over a unit of time, directly related to the half-life of the isotope.

Neutron decay

A type of radioactive decay in which a neutron is transformed into a proton, an electron, and an antineutrino, commonly occurring in unstable isotopes.

Proton decay

A hypothetical type of radioactive decay in which a proton decays into a lighter subatomic particle, often considered as a rare event in some grand unified theories of particle physics.

Electron capture

A process where an electron from the innermost energy level is captured by a proton in the nucleus, resulting in the formation of a neutron and the emission of a neutrino. This decay mode occurs in certain unstable isotopes.