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- absolute zero - a theoretical condition concerning a system at zero Kelvin where a system does not emit or absorb energy (all atoms are at rest)
- accuracy - how close a value is to the actual or true value; also see precision
- acid - a compound that, when dissolved in water, gives a pH of less than 7.0 or a compound that donates a hydrogen ion
- acid anhydride - a compound with two acyl groups bound to a single oxygen atom
- acid dissociation constant - an equilibrium constant for the dissociation of a weak acid
- actinides - the fifteen chemical elements that are between actinium (89) and lawrencium (103)
- activated complex - a structure that forms because of a collision between molecules while new bonds are formed
- activation energy
- activity series
- actual yield
- addition reaction - within organic chemistry, when two or more molecules combine to make a larger one
- aeration - the mixing of air into a liquid or solid
- alkali metals - the metals of Group 1 on the periodic table
- alkaline earth metals - the metals of Group 2 on the periodic table
- allomer - a substance that has different composition than another, but has the same crystalline structure
- allotropy - elements that can have different structures (and therefore different forms), such as Carbon (diamonds, graphite, and fullerene)
- anion - negatively charge ions
- anode
- aromaticity - chemical property of conjugated rings that results in unusual stability. See also benzene.
- atom - a chemical element in its smallest form, and is made up of neutrons and protons within the nucleus and electrons circling the nucleus
- atomic mass unit
- atomic number - the number representing an element which corresponds with the number of protons within the nucleus
- atomic orbital - the region where the electron of the atom may be found
- atomic radius
- average atomic mass
- Avogadro's law
- Avogadro's number
Read more about this topic: Glossary Of Chemistry Terms