qualitative analysis – Qualitative analysis is the methods used to determine the of the nature of the chemical species in a sample. Methods to answer the question “What is it?”
Example: Dr. Labguy used qualitative analysis to determine the sample contained silver.

quantitative analysis – Quantitative analysis refers to the determination of how much of a given component is present in a sample. Methods to answer the question “How much?”
Example: Dr. Labguy used quantitative analysis to determine the sample contained 46.3% silver by mass.

quantum – A quantum is a discrete packet of energy or matter. Quantum also means the minimum value of a physical property involved in an interaction.

quantum mechanics – The physical science used to calculate and analyze the energies and spatial distributions of small particles confined to very small regions of space.

quantum number – A number used when describing the energy levels available to atoms and molecules. An electron in an atom or ion has four quantum numbers to describe its state.
There are four quantum numbers:
n – describes the energy level
ℓ – describes the subshell
mℓ – describes the orbital of the subshell
ms – describes the spin

quantum theory – The general theory which describes the allowed energies of atoms and molecules.

quaternary amine – A quaternary amine is an amine with four carbon atoms bonded to the amine nitrogen. The nitrogen atom of a quaternary amine is a positively charged cation. Quaternary amines are formed from ammonium salt cations. Quaternary amines are often denoted by the shorthand notation 4° amine.

quaternary carbon – A quaternary carbon refers to a carbon atom in a molecule or moiety bonded to four other carbon atoms. Quaternary carbon is often expressed in shorthand notation as 4° carbon.

quicklime – Quicklime is a common name for the compound calcium oxide, CaO.
Also known as: calcium oxide, burnt lime

quicksilver – Quicksilver is an alchemical name and common name for the element mercury.
Also known as: mercury, hydrargyrum