Acid: Substances which, as defined by Brønsted-Lowry theory, donate a proton to a base in a chemical reaction.

Anion: An ion with negative charge.

Atom: The basic unit of elements and fundamental building blocks of matter.

Atomic number: Number that represents the identity of an atom based on the number of protons in its nucleus and determines its position on the periodic table.

Atomic weight: Average mass of an atom of an element as it occurs in nature expressed in atomic mass units.

Aufbau principle: Also called building-up principle, a principle stating the in the ground state of atoms, electrons fill subshells of lowest energy levels first.

Base: Substances which, as defined by Brønsted-Lowry theory, receive a proton from an acid in a chemical reaction.

Buffer solution: Solutions that resist large changes in pH upon addition of acids or bases.

Cation: An ion with positive charge.

Chemical equilibrium: The state in which the rate of forward and reverse reactions in a reversible chemical reaction are equal.

Colligative properties: Properties of solutions that depend on the concentration of solutes in the solution.

Colloid: A mixture where microscopic insoluble particles with diameter between 1 nanometer and 1 micrometer are dispersed throughout another substance.

Combustion reaction: A reaction that involves a fuel reacting with an oxidant, releasing energy and usually forming water and carbon dioxide.

Covalent bond: A chemical bond that involves sharing of electron between atoms.

Critical point: A point in a phase diagram that specifies the certain temperature and pressure in which matter ceases to be distinguishable from being a liquid and gas and transitions to become a supercritical fluid.

Electron: A negatively-charged subatomic particle.

Element: A substance consisting of atoms with the same number of protons.

Enthalpy: The internal energy required to generate a chemical reaction and the energy required to create a certain pressure and volume for the process to take place.

Entropy: The unavailability of thermal energy within a system to be converted into mechanical work, degree of randomness within a system.

Excess reagent: Also called excess reactants, leftover reactants after a chemical reaction occurs and limiting reactants are used up.

First law of thermodynamics: The law that states that energy cannot be created nor destroyed, but can be transformed into other forms.

Functional groups: Specific groups of atoms within a molecule who have their own properties and participates in the same chemical reactions for all functional groups of the same type.

Gibbs Free Energy: maximum amount of work that can be performed in a closed space at a certain temperature and pressure.

Heterogeneous mixture: A non-uniform mixture of substances with components visible to naked eye.

Homogeneous mixture: Mixtures with uniform composition.

Hund’s rule: The rule stating that every orbital in a sublevel must be occupied with at least one electron first before an orbital can host two electrons.

Ideal Gas Law: The law stating that the pressure of an ideal gas is directly proportional to its temperature and its number of molecules and inversely proportional to its volume.

Ion: An atom or molecule with a net electric charge due to difference in the number of protons and electrons within the atom or molecule.

Ionic bond: A chemical bond that involves transfer of electrons between atoms.

Isotope: Atoms of the same element with the same number of protons but different number of neutrons.

IUPAC: International Union of Pure and Applied Chemistry, a global organization responsible for developing the standard nomenclature for chemical compounds.

Kinetic-molecular Theory: The theory stating that all matter consist of tiny, constantly-moving particles whose kinetic energy determine their phase.

Mixture: A composition of two or more substances.

Molar mass: The mass of one mole of a substance, expressed in grams per mole.

Mole: A unit equivalent to 6.022 x 10^23 particles.

Neutron: A subatomic particle with no charge. 

Octet rule: A rule stating that elements tend to bond in a way that they have eight valence electrons in their outer shell.

Organic compound: A compound containing primarily of carbon covalently bonded with hydrogen. 

Oxidation: chemical reaction involving loss of electrons, increasing its oxidation state.

Oxidation number: also called oxidation state; number that represents the net charge of an atom based on the number of electrons gained or lost by that atom.

Pauli Exclusion Principle: A principle stating that all electrons in an atom have their own sets of quantum numbers, or electrons occupying the same orbital must have opposite spins.

Periodic table: Also called periodic table of elements, visualization of elements ordered into rows and columns.

pH: A logarithmic scale measuring the acidity or basicity of a solution, based on the concentration of hydrogen ions within the solution.

Phase diagram: A diagram showing the states of matter in which a substance exist at a particular temperature and pressure.

Product: Substances formed in a chemical reaction.

Proton: Subatomic particle with positive charge.

Rate of reaction: The rate at which a substance is consumed or formed in a chemical reaction, expressed as change in concentration over time.

Reactant: Substances that combine together to form products in a chemical reaction.
Redox reaction: chemical reaction that involves transfer of electrons, resulting to change in oxidation numbers.

Reduction: A chemical reaction involving gain of electrons, reducing the oxidation state of the substance.

Second law of thermodynamics: A law that states that the entropy of an isolated system always increases or remains constant in an ideal, reversible process.

Spontaneous: Chemical reactions that occur naturally, without external energy input.

Solution: A homogeneous solution where one substance is fully dissolved in another, forming a uniform mixture.

Stoichiometry: Study of the relationship of the quantities of reactants and products in a chemical reaction.

Supercritical fluid: A fluid existing above the critical point which cannot be distinguished as liquid or gas.

Surface tension: The tendency of a fluid at rest to shrink into the minimum surface area available.

Suspension: A heterogeneous mixture containing particles greater than 1 micrometer which do not dissolve, forming a non-uniform appearance.

Triple point: A point in a phase diagram that specifies the pressure and temperature in which a substance exists as both solid, liquid, and gas.

Vapor pressure: Pressure exerted by a vapor in thermodynamic equilibrium to its liquid or solid counterpart.

Viscosity: Property of a fluid to resist flow.

Law of Conservation of Mass: The law stating that in a closed system, matter cannot be created nor destroyed by physical or chemical changes.

Le Chatelier’s principle: The principle stating a system in chemical equilibrium will shift to undo a disturbance done upon the system.

Lewis structure: A visual representation that shows valence electrons using dots and covalent and ionic bonds using lines.

Limiting reagent: also called limiting reactant, reactants that is being completely consumed first in a chemical reaction, limiting the amount of products formed.