U3 definitions

Covalent bond

Simultaneous electrostatic attraction between a pair of electrons and positively charged nuclei. Usually forms between non-metals.

Electronegativity

A measure of the tendency of an atom to attract a shared electron pair to itself

Octet rule

A stable electron configuration of 8 electrons in the valance shell, as nobe gases do.

Bond enthalpy

Energy required to break one mole of a given type of bond

Co-ordinate/ dative covalent bond

Both electrons in a shared electron pair are provided by one of the two atoms in the bond.

Electron domain

Each VSEPR electron pair within the same region (e.g. double bond is one ED)

Volume

Amount of space occupied

Pressure

Force applied per unit area

Temperature

Average kinetic energy of the particles in a substance

Boyle’s law

Pressure and volume of inversely proportional

Charles’ law

Volume and temperature are directly proportional

Gay-Lussac law

Pressure and temperature are directly proportional

Avogadro law

Volume and number of moles are directly proportional

Localized electrons

Electron pair that is held in a specific position in the molecule, usually between 2 atoms in a single bond

Delocalized electrons

Electron pair in a bond placed in different positions within the molecule or polyatomic ion

Resonance structures

The multiple structures a moelcule can be drawn in when the electrons delocalizes over several atoms

Intermediate bond

Blend of properties between different types of bonds ( e.g. single and double bond)

Bond order

Measure of number of chemical bonds between a pair of atoms

Radicals

A chemical species tha tcontains an unpaired electron. Is high enthalpy, high reactivity and shor tlfietime.

Reaction mechanism

A series of small steps that make up a chemical reaction of how substances are converted into other substances.

Susbtitution reaction

Replacement of an atom/group bonded to a C atom with another atom/group

Homolytic fission

The two electrons in a bonding electron pair each move to a different atom. When the bond breaks. Forms free radicals.

Initiation

Formation of a reactive free radical, by exposing halogens to uv light

Propagation

a series of steps where free radicals are formed and used in later steps. Can also regenerate the free radical formed in the initiation step, so the reaction can keep continuing

Termination

Reaction between two free radicals to form a stable compound