Module 2 defintions

Bond

the force that holds two atoms together in a compound

Bond angle

the angle formed across two adjacent bonds in a molecule

Bond energy

the energy required to break a given chemical bond

Bonding pair

an electron pair found in the space between two atoms

Condensation

the process by which vapour molecule re-form a liquid

Covalent bonding

bonding in which atoms share electrons

Dipole-dipole attraction

the attractive force resulting when polar molecules line up such that the positive and negative ends are close to each other

Dipole moment

a property of a molecule whereby the charge distribution can be represented by a centre of positive charge and a centre of negative charge

Double bond

a bond in which two atoms share two pairs of electrons

Duet rule

the observation that some molecules form in which the atoms combine in such a way as to have two electrons in their valence shells

Electronegativity

the tendency of an atom in a molecule to attract shared electrons to itself

Hydrogen bonding

unusually strong dipole-dipole attractions that occur among molecules in which hydrogen is bonded to a highly electronegative atom

Intermolecular forces

relatively weak interactions that occur between molecules

Intramolecular forces

interactions that occur within a given molecule

Ionic bonding

the attraction between oppositely charged ions

Ionic compound

a compound that results when a metal reacts with a non-metal to form cations and anions

Lewis structure

a diagram of a molecule showing how the valence electrons are arranged among the atoms in the molecule

London dispersion forces

the relatively weak forces, which exist among noble gas atoms and nonpolar molecules that involve an accidental dipole that induces a momentary dipole in a neighbour

Lone pair (unshared pair)

electron pairs that are localised on a given atom; electron pairs not involved in bonding

Molar heat of fusion

the energy required to melt 1 mole of a solid

Molar heat of vapourization

the energy required to vapourize 1 mole of liquid

Molecular structure / geometric structure

the three-dimensional arrangement of atoms in a molecule

Octet rule

the observation that atoms of non-metals form the most stable molecules when they are surrounded by eight electrons

Polar covalent bond

a covalent bond in which the electrons are not shared equally because one atom attracts them more strongly than the other

Resonance

a condition occurring when more than one valid Lewis structure can be written for a particular molecule. The actual electron structure is represented not by any one of the Lewis structures but by the average of all of them

Single bond

a bond in which two atoms share one pair of electrons

Triple bond

a bond in which two atoms share three pairs of electrons

Valance shell electron pair repulsion (VSEPR) model

a model the main postulate of which is that the structure around a given atom in a molecule is determined principally by the tendency to minimize electron pair repulsion

Vapourization / evapouration

the process in which a liquid is converted to a gas

Vapour pressure

the pressure of the vapour over a liquid at equilibrium in a closed container