Simia

Acid

A substance that donates hydrogen ions (protons) or accepts an electron pair in chemical reactions, typically having a pH less than 7.

Activation Energy

The minimum amount of energy required to initiate a chemical reaction.

Atom

The basic unit of a chemical element, consisting of a nucleus of protons and neutrons with electrons orbiting it.

Atomic Mass

The mass of an atom of a chemical element expressed in atomic mass units.

Base

A substance that accepts hydrogen ions (protons) or donates an electron pair, typically having a pH greater than 7.

Bond (Chemical)

A lasting attraction between atoms, ions, or molecules that enables the formation of chemical compounds.

Catalyst

A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Compound

A substance formed when two or more chemical elements are chemically bonded together.

Covalent Bond

A chemical bond that involves the sharing of electron pairs between atoms.

Electrolysis

A technique that uses direct electric current to drive an otherwise non-spontaneous chemical reaction.

Electron

A stable subatomic particle with a negative electrical charge, found in all atoms.

Element

A pure substance consisting only of atoms that all have the same numbers of protons in their atomic nuclei.

Endothermic Reaction

A chemical reaction that absorbs energy from its surroundings, usually in the form of heat.

Exothermic Reaction

A chemical reaction that releases energy into its surroundings, usually in the form of heat or light.

Ion

An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Ionic Bond

A type of chemical bond that involves the electrostatic attraction between oppositely charged ions.

Isotope

Variants of a particular chemical element which differ in neutron number, and consequently in nucleon number.

Mole

The SI unit for the amount of substance, equal to approximately $6.022 \times 10^{23}$ particles (Avogadro's number).

Molecule

A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound.

Neutron

A subatomic particle of about the same mass as a proton but without an electric charge.

Oxidation

A process involving the loss of electrons during a reaction by a molecule, atom, or ion.

Periodic Table

A tabular display of the chemical elements, organized by atomic number, electron configuration, and recurring chemical properties.

pH Scale

A scale used to specify the acidity or basicity of an aqueous solution.

Proton

A stable subatomic particle occurring in all atomic nuclei, with a positive electric charge.

Reduction

A process involving the gain of electrons during a reaction by a molecule, atom, or ion.

Solution

A homogeneous mixture composed of two or more substances, where a solute is dissolved in a solvent.

Valence Electrons

An outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond.