Critical Mass

The minimum amount of fissile material needed to maintain a nuclear chain reaction.

Heat of Reaction

The change in the enthalpy of a chemical reaction that occurs at a constant pressure.

Transuranium Element

Elements with more than 92 protons in their nuclei.


The proton and the Neutron.

Alpha Particle

2 protons and 2 neutrons bond together.

Free Energy (G)

Combined enthalpy and entropy of a system.

Mass Defect

Difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons.

Electron Capture

Inner orbital electron is captured by the nucleus of its own atom.

Chain Reaction

Reaction in which material that starts the reaction is also one of the products that can start another reaction.

Octane Rating

Measure of its burning efficiency.

Beta Particle

An electron emitted from nucleus during some kinds of radioactive decay.

Radioactive Tracer

Radioactive atoms that are incorporated into substance so that movement of the substance can be followed by radiation detectors.

Band of Stability

Stable nuclei cluster over a range of neutron-proton ratio.

Activation Energy (Ea)

Minimum energy for a reaction to occur or to transform the reactants into an activated complex.

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