chemistry

Valence electrons

The total number of electrons that are found in the outermost energy level of an atom

Valency

The number of electrons an atom must gain, lose or share in order to achieve a full outermost energy level

Group number

Represents the total number of valance electrons that an atom has in its outermost energy level

Ionisation

The reaction of a molecular substance with water to produce

Polyatomic ions

Ions which are made up of combinations of two or more atoms that carry an overall charge

Intramolecular bond

The bond which occurs between atoms within molecules

Covalent bond

Involves the sharing of at least one pair of electrons by two atoms

Non-polar bond

Formed when electrons are equally shared due to a zero difference in electronegativity

Polar covalent bond

Occurs when electrons are unequally shared due to a difference in electronegativity

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons

Lone pairs

Electron pairs in the outermost energy level of an atom that do not take part in the chemical bonding process

Dative covalent bond

Forms when a lone pair of electrons from one attempt is shared with another atom which has an empty orbital in its outermost energy level

Ionic bond

Involves a transfer of electrons to form cations and anions which are electrostatically attracted in an ionic crystal lattice

Cation

A positive ion

Anion

A negative ion

Metallic bond

The attraction between positive kernels and a sea of delocalized electrons

VSEPR theory

A model used, in chemistry, to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms

Heat of a reaction

The net change of chemical potential potential energy of a system

Exothermic reactions

Reactions which transform chemical potential energy into thermal energy

Endothermic reactions

Reactions which transform thermal energy into chemical potential energy

Activation energy

The minimum energy required to start a chemical reaction

Activated complex

A high energy, unstable transition state between the reactants and the products

Heat

A form of energy. Often referred to as thermal energy and it is measured in Joules

Catalyst

A substance that increases the rate of the reaction but remains unchanged at the end of the reaction

Dissociation

The splitting of an ionic compound into i

Electrolyte

A substance that can conduct electricity dueto the presence of free ions when molten or dissolved in solution

Temperature

The average kinetic energy of particles of a substance, measured in Celsius