Activation Energy

The minimum energy that a particle needs in order to react: the energy (enthalpy) difference between the reactants and the transition state.

Aldehyde

An organic compound with the general formula RCHO in which there is a C=O double bond.

Alkaline Earth Metals

The metals in group two of the periodic table.

Alkane

A hydrocarbon with C-C and C-H single bonds only.

With the general Formula C_nH_2n+2

Allotropes

Pure elements which can exist in different forms in which their atoms are arranged differently.

For example Diamond and Graphite are allotropes of Carbon

Anaerobic Respiration

The process by which energy is released and new compounds formed in living thims in the absence of oxygen.

Atom Economy

This describes the efficiency of a chemical reaction by comaring the total number of atoms in the product with the total number of atoms in the reactants.

Mass of Desired Product _x100 =% Atom Economy 

Total mass of reactants                                    

Atom Orbital

A region of space around an atomic nucleus where ther is a high probability of finding an electron

Bond Dissociation Enthalpy

The enthalpy change required to break a covalent break a covalent bond with all species in a gaseous space.

Calorimeter

An instrument for measureing the heat changes that accompant chemical reactions.

Catalyst

A substance that alters the rate of a chemical reaaction but is not used up in the reaction.

Catalytic Cracking

The breaking, with the aid of the catalyst, of a long chain alkane molecules (obtained from crude oil) into shorted chained hydrocarbons some of which are alkenes.

Carbocations

An organic ion in hich one of the carbon atoms has a positive charge.

Carbon-neutral

A process, or series of processes in which as much carbon dioxide is absorbed from the atmosphere as is given out.

Chemical Feedstock

The starting materials in an inductrial chemical reaction.

Co-ordinate bonding

Covalent bonding when both the electrons in the bond come from one of the atoms in the bond.

(Also called dative-covalent)

Covalent Bonding

Describes a chemical bond between two non-metal elements, in which a pair of electrons are shared between each element.

Cracking

The breaking of long chain alkanes molecules into shorter chain hydrocarbons.

Dative-Covalent Bonding

Covalent bonding when both the electrons in the bond come from one of the atoms in the bond.

(Also called Co-ordinate bonding)

Avogadro Constant

The total number of Particles in a mole of a substance. 

6.022x10²³

Delocalised

Describes electrons that are spread over several atoms to help the bond together.

Dipole-Dipole Force

An intermolecular force that results from the attraction between molecules with permanent dipoles.

Displacement Reaction

A chemical reaction in which one atom or group of atoms replaces another in a compound, for example

Zn +CuO → ZnO + Cu

Displayed Formula

The formula of a compound drawn out so that each atom and each bond is shown.

Example:

Disproportionation

Describes a redox reaction in which the  oxidation number if some atoms of a particular element increases and that of other atoms of the same element decreases.

Dynamic Equilibrium

A situation in which the composition of a reaction mixture does not change because both the forward and backwards reactions are occuring at the same rate.

Electron Density

The probability of an electronbeing found in a particular volume or space.

Electron Pair Repulsion Theory

A theory which explains the shapes of simple molecules by assuming that pairs of electrons around a central atom replel each other and thus take up positions as far away from each other as possible.

Electronegativity

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

Electrophile

An electron-deficient atom, ion or molecule that takes part in an organic reaction by attacking areas of high elctron density in another reactant.

Electrophillic Addition

A reaction in which a C=C Double bond is saturated and in which the initial reaction is an attack by an electrophile.

Electrostatic Forces

The forces of attraction and repulsion between electrically charged particles.

Elimination

A reaction in which an atom or group of atoms is removed from a reactant.

Empirical Formula

The simplest whole number ratio in which the atoms in a compound combine together.

Endothermic

Describes a reaction in which heat is take in as the reactant change to products; the temperature of the surrounding drops.

Enthalpy Change

A measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure.

Enthalpy Diagrams

Diagrams in which the epthalpys (energies) of the reactants and products of a chemical reaction are plotted on a vertical scale to show their relative levels

Equilibrium Mixture

The Mixture of reactants and products formed when a reversible reaction is allowed to proceed in a close system until no further change occurs. The forward and backward reactions are still proceeding but at an equal rate.

Exothermic

Describes a reaction in which heat is given out as the reactant change to products; the temperature of the surrounding rises.

Fingerprint Region

The area of an infrared spectrum below about 1500cm^-1. It is caused by complex vibrations of the whole molecule and is characteristic of a particular molecule.

Fraction

A mixture of hydrocarbons collected over a particular range of bp's during the fraction distillation of crude oil.

Free Radical

A chemical species which an unpaired electron - usually highly reactive.

Functional Group

An atom or group of atoms in an organic molecule which is responsable for the characteristic reaction of that molecule.

Group

A vertical column of elements in the periodic table. The elements have similar properties because the same outer electron arangement.

Half Equation

An equation for a redox reaction which considers just one of the species involved and show explicitly the electrons transferred to or from it.

Heterogeneous Catalyst

A catalyst which is in a different phasefrom the reactants. For example, Iron(s) in the Haber preccess Cinversion of Nitrogen_(g) and hydrogen_(g) to ammonia.

Homogeneous Catalyst

A catalyst which is in the same phase as the reactants.

Homologeous Series

A series which is a set of organic compounds whoch the same functional group. The compounds differ in the length of their hydrocarbon chains.

Hydrogen Bonding

A type of intermolecular force in whch a hydrogen atom covalently bined to an electronegative atom.

NOF!!!

Incomplete Combustion

A combustion reaction in which there is insufficient oxygen for all the carbon in the fuel to burn to CO_2. CO and/or C (soot) are formed.

Ionic Bonding

Describes a chemical bond between a metal and a non-metal in which an electron or electrons are transfered from the metal to the non-metal, resulting in the formation of oppositly charges ions hich electrostatic forces of attraction between them.

Ionisation Energy

The energy required to remove a mole of electrons from a mole of isolated gaseous atoms or ions.

Isomer

One (Or more) compounds with the same molecular formula but differen structural formula.

Ie : The same Atoms are arranged differently in space.

Ketone

An organic compound with the general formula R₂CO in which there is a C=O double bond.

Seconday Alcohol Oxidation.

Lattice

A regular 3D arrangement of atoms, ions or molecules

Eg. Macromolecular

Leaving Group

In an organic substitution reaction from a believing group is an atom or group of atoms that is ejected from the starting material, normally taking with it an electron pair and forming a negative ion.

Lone Pair

A pair of electrons in the outer shell of an atom that is not involved in bonding, also called an unshared pair.

Used in a dative-covalent bond.

Maxwel-Boltzmann Distribution

The distribution of energies (and therfore speed) of the molecules in a gas or liquid.

Mean Bond Enthalpy

The average value of the bond dissociation enthalpy for a given type of bond taken froma range of different compounds.

Metallic Bonding

Describes a chemical bond in which out electrons are spread over a lattice of metal ions in a delocalised system.

Mole

A quantity of a substance that contains the advogadro's constant (6.022x10²³) of particals (eg. Atoms, molecules or Ions)

Molecular Formula

A formula that tells us the numbers of atoms of each different element that makes up a molecule of a compound.

Molecular Ion

In mass spectrometery this a molecule of the sample which has been ionised but which has not broken up during its flight through an instrument.

Monomer

A small molecule that combines with many other monomer a polymer.

Nucleons

Protons and neutrons - the sub-atomic particles nuclei of atoms.

Nucleophile

An ion or group of atoms with a negative charge or a partically negative - charged area that takes part in an organic reaction by attackin an electron - deficient area in another reactant.

Neucleaphillic Substitution

Nucleus

The tiny positively charged center of an atom composed of Protons and Neutrons.

Oxidation

A reaction in which an atom or group of atoms loses electrons.

Oxidation State

The number of electrons lost or gained by an atom in a compound compared ot the uncombined atom. It forms the basis of a way  keeping track of redox (electronic transfer) reactions. Also called Oxidation number.

Oxidising Agent

A reagent thaat oxidises (removes electron from) another species.

Percentage Yeild

In a chemical reaction, this is the actual amount of product produced, divided by the theoretical yeild (predicted from the chemical equation) expressed as a %.

Period

A horizontal row of elements in the periodic table. There are trends in the properties as we go across the period.

Periodicity

The regualr occurance of the properties of element when the are aranged in atomic number order as in the periodic table.

Polar

Describes a molecule in which the charge is not symetrically distributed so that one area is slightly charged and another slightly negatively charged.

Positive Inductive Effect

Describes the tendance of some atoms or groups of atoms to release electrons via a covalent bond.

Proton Number

The number of protons in the nucleus of an atom; the same as the atomic number (z)

Redox Reaction

Short for Reduction - Oxidation reasction, it describes reactions in which electrons are transfered from one species to another.

Reducing Agent

A reagent that reduces (Adds electrons too) another species.

Reduction

A reduction in which or group of atoms gains electrons.

Relative Atomic Mass  (A_r)

A_r = Adverage mass of Molecule

        ¹/₁₂ ^th mass of Carbon