Physics p2 June

melting point

temperature at which the solid state and liquid state of a substance are in equilibrium

Boiling point

temperature at which the vapour pressure of a substance is equal to the atmospheric pressure

vapour pressure

pressure experienced by a vapour of a substance in equilibrium with the liquid

substances with strong intermolecular forces have:

high melting and boiling points with low vapour pressure

AX’2; E’0

linear

AX’3; E’0

Trigonal planar

AX4’; E’0

Tetrahedral

AX’5; E’0

trigonal bypyramidal

AX’6; E’0

Octahedral

AX’2; E’2

Bent/angular/v-shape

AX’3; E’1

Trigonal pyramidal

Strongest intermolecular force

hydrogen bond

weakest intermolecular force

London forces

ion dipole force

occurs when a dipole approaches a positive or negative ion

ion induced dipole forces

an ion affects the electron cloud around an atom or molecule when nearby causing a temporary dipole

dipole dipole forces

attraction between slightly positive atom in a polar molecule and another polar molecule

dipole induced dipole forces

a polar molecule can induce a temporary dipole in a non polar molecule or atom

induced dipole/ London forces/ dispersion

when two non polar atoms of noble gasses or molecules approach each other, there's a slight rearrangement of their electron clouds, A weak, short, temporary dipole is formed, which comes and goes and alters direction

hydrogen bond

This is an exceptionally strong dipole dipole force in comparison with other Van Der Waals forces. it occurs between molecules in which hydrogen is bonded to nitrogen, oxygen or flourine

interatomic forces

bonds that hold different atoms together in a molecule

Density

number of particles per unit volume

viscosity

an indication of a liquids resistance to flow (high viscosity liquids don't flow easily)

thermal expansion

means the material expand on heating

Covalent thermal conductivity

no free electrons to help transmit heat

metalic thermal conductivity

valence electrons are free to help with the conduction of heat

solubility of a substance

is a measure of how easily a substance can dissolve in another substance

Like dissolves like

substances with the same intermolecular forces dissolve one another

Electronegativity

measure of the ability of an atom to attract a bonded pair of electrons

chemical bonding

the mutual attraction between two atoms resulting from a simultaneous attraction between their nuclei and outer shell

covalent bond

two non metal atoms in a molecule share an electron pair during the overlapping of orbitals to form a molecule

non polar covalent bond

electron density is shared equally between the atoms, the shared electron pair is distributed evenly between the two atoms where the orbitals overlap

polar covalent bond

bond in which electron density is shared unequally between the atoms, the shared electron pair is distributed unevenly between the two atoms where the orbitals overlap

molecule

group of two or more atoms covalently bonded which function as a neutral unit

ionic bond

bond between metal atoms and non metal atoms if electrons are transferred from a metal atom to a non metal atom

metalic bond

bond between metal atoms through the attractive forces between delocalised electrons and the crystal lattice of a positively charged atom rest

valence electrons

electrons found in the outermost energy level

dative covalent bonds

covalent bonds between atoms where one atom provides both electrons that are sharef

octet rule

all atoms with the exception of hydrogen and helium try to have eight electrons, in four pairs of two, surrounding them to achieve noble gas structure

VSERP

model used to predict the shape of a molecule

shape of a molecule depends on

the type of bond, number of electron pairs around the central atom and the lone pairs

Bond energy

energy needed to break one mole of a compounds molecules into seperate atoms

bond length

distance between the nuclei of the two atoms that are bonded