Glossary
Atomic mass unit (amu or u)
A standard unit of mass used to express atomic and molecular masses, defined as 1/12th the mass of a carbon-12 atom.
Example:
The mass of a proton is approximately 1.007 atomic mass unit (amu or u), a convenient scale for subatomic particles.
Binding Energy
The energy required to separate a nucleus into its individual constituent protons and neutrons, or the energy released when a nucleus is formed from its nucleons. It indicates nuclear stability.
Example:
Iron-56 has one of the highest average Binding Energy per nucleon, making it one of the most stable nuclei in the universe.
E (energy)
The capacity to do work, often released or absorbed during nuclear reactions as a result of mass changes.
Example:
When a nucleus undergoes fission, a tremendous amount of E (energy) is released, which can be harnessed in power plants.
Fission
A nuclear reaction in which a heavy, unstable nucleus splits into two or more smaller nuclei, typically initiated by absorbing a neutron, releasing a large amount of energy.
Example:
Nuclear power plants generate electricity by controlling the chain reactions of uranium Fission.
Fusion
A nuclear reaction in which two light nuclei combine to form a heavier, more stable nucleus, releasing an even greater amount of energy than fission.
Example:
The immense heat and light from the Sun are powered by continuous Fusion reactions, primarily converting hydrogen into helium.
Mass Defect (Δm for binding energy)
The difference between the total mass of the individual nucleons (protons and neutrons) and the actual measured mass of the nucleus they form. This 'missing' mass is converted into binding energy.
Example:
When calculating the Mass Defect for a helium nucleus, you'll find its actual mass is slightly less than the sum of its two protons and two neutrons, indicating the mass converted into binding energy.
Mass number (A)
The total number of protons and neutrons (nucleons) in an atomic nucleus, representing the approximate atomic mass of the isotope.
Example:
In Carbon-14, the Mass number (A) is 14, indicating it has 6 protons and 8 neutrons.
Mass-Energy Equivalence (E=mc²)
Einstein's principle stating that mass and energy are interchangeable, meaning a small amount of mass can be converted into a large amount of energy, and vice versa.
Example:
The immense power of a nuclear bomb demonstrates Mass-Energy Equivalence, where a tiny fraction of mass is converted into explosive energy.
Nucleons
The collective term for the particles found in an atomic nucleus, specifically protons and neutrons.
Example:
The Nucleons within a nucleus are held together by the strong nuclear force, overcoming the electrostatic repulsion between protons.
c (speed of light)
A fundamental physical constant representing the speed at which light and all other electromagnetic waves travel in a vacuum, approximately 3 x 10⁸ m/s.
Example:
The 'c' in E=mc² is squared, highlighting how even a small amount of mass can yield enormous energy due to the incredibly high value of the c (speed of light).
Δm (delta m)
Represents the change in mass in the context of mass-energy equivalence, which is converted into or from energy during a nuclear reaction.
Example:
In a nuclear reaction, if the products have slightly less mass than the reactants, that missing Δm is the mass converted into released energy.