Glossary

A - E of a Chemistry Glossary. All the terms come from the gloassary of this book. You can download the entire glossary file from here.

A

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.

Allotropes -
Pure elements which can exist in different physical forms in which their atoms are arranged differently. For example, diamond, graphite and buckminsterfullerene are allotropes of carbon.

Anions -
Negatively charged ions.

Atomic Number (Proton Number) -
The number of protons in the nucleus of an atom. Also the order of an element in the Periodic Table.

Average Bond Enthalpy -
The amount of enthalpy (energy) that has to be put in to break a specicfied chemical bond. It is an average value for the specified bond in a number of different compounds.

B

Biodegradeable -
A substances is biodegradeable if it breaks down naturally in the environment under the action of microorganisms, enzymes etc

C

Calorimeter -
An instrument for measuring the heat changes that accompany chemical reactions.

Carbanion -
An organic ion in which one of the carbon atoms has a negative charge.

Carbocation -
An organic ion in which one of the carbon atoms has a positive charge.

Carboxylic Acids -
Organic compounds with the general formula RCOOH in which there is a C=O double bond and an -OH group on the same carbon atom.

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

Cations -
Positively charged ions.

Chain Reaction -
A reaction with several steps involving free radicals.

Complex Ions -
Ions with more than one atom covalently bonded together.

Coordinate Bonding -
Covalnet bonding in which both the electrons in the bond come from one of the atoms in the bond (also called dative covalent bonding).

Cracking -
The breaking of long-chain alkane molecules (obtained from crude oil) into shorter chain hydrocarbons, some of which are alkenes.

Covalent Bonding -
A type of bonding between non-metal atoms that is the result of electrons being shared between the atoms.

D

Dative Covalent Bonding -
Covalent bonding in which both the electrons in the bond come from one of the atoms in the bond (also called coordinate bonding).

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

E

Electron -
A negatively charged sub-atomic particle that is found at some distance from the nucleas of an atoms.

Electron Pair Repulsion Theory -
A theory which explains the shapes of simple molecules by assuming that groups of electrons around a central atom repel each other and thus take up positions as far away as posible from each other in space.

Electronegativity -
The ability of an atom to attract the electrons in covalent bonds towards itself.

Electrophile -
A reagent that attacks electron-rich areas in an organic molecule (such as carbon-carbon double bond).

Electrostatic Forces -
The forces of attraction and repulsion between electrically charged particles.

Elimination Reaction -
A reaction in which a small molecule such as water or hydrogen chloride is ejected from the reactants.

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

Endothermic -
Describes a reaction in which heat is taken in as the reactants change to products - the temperature thus drops.

Energy Density -
Describes the amount of energy stored per kilogram by a fuel. This energy can be released by burning the fuel.

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

Entity -
The simplest forumla unit of a compound.

Exothermic -
Describes a reaction in which heat is given out as the reactants change to products - the temperature thus rises.