Chemistry Glossary

A substance that releases hydrogen ions in aqueous solution (a proton donor)

A base that is soluble in water and releases hydroxide ions in aqueous solution

A salt that doesn't contain any water of crystallisation.

A neutral particle made up of protons and neutrons in a central nucleus, and electrons orbiting the nucleus.

The proportion of reactant atoms that become a part of the desired product, expressed as a percentage.

The number of protons in the nucleus.

The distance between the nucleus of an atom and it's outermost electrons.

The energy needed to break one mole of a bond in the gas phase, averaged over the different compounds that the bond is found in.

The number of particles in one mole of substance; 6.02 x 10^23

An equation that has the same number of each type of atom and the same overall charge on each side.

A substance that removes hydrogen ions from an aqueous solution (a proton acceptor)

A model for the structure of an atom proposed by Niels Bohr. He suggested that electrons only exist in fixed orbitals (shells) and not anywhere else.

The energy required to break a bond between two atoms. Usually given as an 'average bond enthalpy' (an average value for the particular bond over the range of compounds it is found in)

The process of breaking a covalent bond

A measure of how many moles (or grams) of a substance are dissolved in a volume of solution.

A covalent bond formed when one atom provides both of the shared electrons.

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

An electron that is not attached to a specific atom.

A difference in charge between two atoms caused by a shift in the electron density in a bond.

A reaction where a more reactive element pushes out (displaces) a less reactive element in an ionic solution.

A way of representing a molecule that shows how all the atoms are arranged and all the bonds between them.

A way of representing a molecule that shows how all the atoms are arranged and all the bonds between them.

When an element is both oxidised and reduced in a single chemical reaction.

A subatomic particle with a relative charge of 1- and a relative mass of 1/2000, located in the orbitals around the nucleus.

A subatomic particle with a relative charge of 1- and a relative mass of 1/2000, located in the orbitals around the nucleus.

The number of electrons that an atom or ion has and how they are arranged.

A region of an atom with a fixed energy that contains electrons orbiting the nucleus.

The theory that in a molecule lone pair/lone pair bond angles are the biggest, lone pair/bonding pair bond angles are the second biggest and bonding pair/bonding pair bond angles are the smallest.

When inner electrons effectively screen the outer electrons from the pull of the nucleus.

The ability of an atom to attract the bonding electrons in a covalent bond.

An electron-pair acceptor.

The formula giving the simplest whole number ratio of atoms to each element in a compound.

The energy needed to remove one mole of electrons from one mole of gaseous atoms.

An algebraic formula that can describe any member of a homologous series of compounds

A structure consisting of a huge network of covalently bonded atoms. Also called a macromolecular structure.

A regular repeated structure made of oppositely charged ions strongly attracted to each other in all directions.

A regular structure consisting of closely packed positive metal ions in a sea of delocalised electrons.

A salt that contains water of crystalisation.

A molecule that only contains hydrogen and carbon atoms.

The strongest intermolecular force. It occurs when polarised covalent bonds cause hydrogen atoms to form weak bonds with lone pairs of electrons on fluorine, nitrogen or oxygen atoms of other molecules.

A substance that changes colour at a certain pH.

A type of intermolecular force caused by temporary dipoles, which causes all atoms and molecules to be attracted to each other. Also called London (dispersion) forces.

Forces between molecules e.g. induced dipole-dipole forces, permanent dipole-dipole forces and hydrogen bonding.

A charged particle formed when one or more electrons are lost or gained by an atom or molecule.

An electrostatic attraction between positive and negative ions.

An equation which only shows the reacting particles of a reaction involving ions.

The removal of one or more electrons from an atom or molecule, resulting in an ion forming.

One of two or more forms of an element with the same number of protons but different numbers of neutrons and masses.

The relative amount of a particular isotope occurring in a sample of an element.

A regular structure made up of atoms or ions.

The total number of protons and neutrons in the nucleus of an atom.

An analytical technique used to find the structure of a molecule by measuring the masses of the ions it produces when it is bombarded with electrons.

A chart produced by a mass spectrometer

A simplified picture or representation of a real physical problem.

The mass of one mole of something.

The ratio of the number of moles of each reactant and product in a balanced chemical equation

The unit of amount of substance. One mole is roughly 6.02 x 10^23 particles (the Avagado constant).

A way of representing molecules that shows the actual number of atoms of each element in a molecule.

An ion made up of a group of atoms with an overall charge.

A small molecule which is used to make a polymer

A reaction between an acid and a base to produce a salt and water

A subatomic particle with a charge of 0 and a relative mass of 1, located in the nucleus of an atom.

An element in Group 0 of the periodic table.These elements are extremely stable because they have a full outer shell.

A model for the structure of an atom proposed by Rutherford. He suggested that atoms consist of small positively charged nucleus, surrounded by a cloud of negatively charged electrons.

An electron-pair donor

The central part of an atom or ion, made up of protons and neutrons.

A region of a sub-shell that contains a maximum of two electrons with opposite spins.

Loss of electrons

The total number of electrons an element has donated or accepted. Also called an oxidation state.

Something that accepts electrons and gets reduced.

The amount of product that is actually obtained during a reaction expressed as a percentage of the amount of product that should form.

The trends in physical and chemical properties of elements as you go across the periodic table.

Intermolecular forced that exist because the difference in electronegativities in a polar bond causes weak electrostatic forces of attraction between molecules.

A model for the structure of an atom proposed by Thomson. He suggested that atoms consist of a positively charged sphere with negatively charged electrons embedded in them.

A covalent bond where a difference in electronegativity has caused a shift in electron density in the bond.

A molecule containing polar bonds that are arranged so that dipoles do not cancel each other out, causing an overall dipole to be created across the molecule.

A long molecule formed from lots of smaller molecules (monomers) joined together.

A subatomic particle with a relative charge of 1+ and a relative mass of 1, located in the nucleus of an atom.

The currently accepted model for the structure of an atom, where particles' positions are predicted by probabilities.

A particle with an unpaired electron.

A reaction where reduction and oxidation happen simultaneously.

Something that donates electrons and gets oxidised.

Gain of electrons

The average mass of an atom of an element compared to 1/12 of the mass of an atom of carbon-12.

The average mass of a molecule or formula unit compared to 1/12 of the mass of an atom of carbon-12

The mass of an atom of an isotope of an element compared to 1/12 of the mass of an atom of carbon-12.

The average mass of a molecule compared to 1/12 of the mass of an atom of carbon-12.

A compound formed when the hydrogen in an acid molecule is replaced by a metal ion or ammonium ion.

A compound with strong covalent bonds within its molecules but weak forces between its molecules

A simplified organic formula which only shows the carbon skeleton and associated functional groups.

A type of momentum possessed by an electron. Spin can either be "down" or "up".

100KPa pressure and a temperature of 298K.

A solution with a precisely known concentration.

A substance's physical state under standard conditions.

A symbol placed after a chemical in an equation that tell you what state of matter it is in.

An acid/base that almost completely ionises in an aqueous solution.

A way of representing molecules that shows the atoms carbon by carbon with the attached hydrogens and functional groups.

A sub-division of an energy-level (shell). Sub-shells may be s,p,d or f sub-shells.

The energy needed to remove 1 mole of each subsequent electron from each ion in 1 mole of positively charged gaseous ions.

A type of experiment used to find concentration of a solution. It involves gradually adding one solution to a known volume of another until the reaction between the two is complete.

A term referring to both induced dipole-dipole interactions and permanent dipole-dipole interactions.

The water contained in an ionic lattice.

An acid/base that only slightly ionises in an aqueous solution.

The amount of product you get from a reaction.

A measure of heat energy in a chemical reaction.