Chemistry

Abelsonite

Abelsonite — a rare nickel porphyrin organic mineral

Absorption

Absorption spectroscopy

Absorption spectroscopy: principles, instruments, and applications

Acanthite

Acanthite — the low‑temperature silver sulfide mineral (Ag2S)

Acetamide

Acetamide (organic compound and rare mineral)

Acetate

Acetate (ethanoate): structure, properties, uses, and biological roles

Acetic acid

Acetic acid (ethanoic acid): properties, uses, and safety

Acetone

Acetone peroxide

Acetone peroxide (APEX): properties, hazards, and forensic significance

Acetonitrile

Acetyl

Acetylcholine

Acetylene

Acetylide

Acid

Acid — definition, properties, examples, and uses

Acid–base reaction

Acid–Base Reaction: Principles, Types, and Applications

Acryl

Acryl: the acryloyl group, acrylic compounds, and their polymers

Actinide

Actinide (series of chemical elements)

Actinium

Activation energy

Addition reaction

Additive

Additive (chemistry and practical uses)

Adenine

Adenosine diphosphate

Adhesion

Adhesive

Adsorption

Aerogel

Aerogel: ultralight, highly insulating porous solids

Aerosol

Aerosol spray

Agonist

Agonist (pharmacology and physiology)

Alabaster

Alabaster: gypsum and calcite varieties, properties and uses

Alanine

Albumin

Alcohol

Alcohol by volume

Alcohol by Volume (ABV): definition, measurement, and typical ranges

Alcoholic proof

Aldehyde

Aldehyde: Structure, Properties, Reactions and Common Uses

Aldol reaction

Aldrin

Aldrin: a persistent organochlorine insecticide

Alexandrite

Alexandrite: the color-change chrysoberyl gemstone

Alkali

Alkali (Water-Soluble Bases): Properties, Examples, and Industrial Uses

Alkali metal

Alkali metals (Group 1 elements)

Alkaline battery

Alkaline battery: chemistry, sizes, history, and common uses

Alkaline earth metal

Alkaline earth metals

Alkaloid

Alkane

Alkene

Alkene (olefin): unsaturated hydrocarbons with carbon–carbon double bonds