Appendix 4.4 Flashcards
LDF
occurs in all molecules
temporary dipoles forming due to uneven e- dispersion
temp dipoles induce other temporary dipoles in neighboring molecules
aolthough temporary dsipoles are always disappearing and reappearing the overall force between the molecules is always attractice because dipoles always induce other ones.
weakest imf
factors affecting LDf strength
increase in e-: the more leectrons, the more bigger the temporray dipoles formed by eneven elecron dispersion. the moer leectrons, the more molecular mass
increase iun e- cloud volume: the larger the volume of the electron cloud, the less strngly outer electrons wil lbe held because the farther leectrons are from the nucleus the less control nuclear charge has on the dispersion of - charge. thi smakes the molecule more polarisable because of bigger dipoles
increasein
relative molecular mass
polarizability
how easily a neutral atom or molecule acquires a temporarily charged pole due to an exterior electric field
mostly influenced by the size of the atom/moleculr or ion
how do permanent dipoles form
a permanent dipole comes in the the form of a polar covalent bond, where the two involved atoms unequally share their electrons because of their elctronegativity difference. the more electronegative atom plls electrons towards itself, creating a partially negtaive charge on itself, and conseuqnetly, a partially positive charge on the other atom
dipole-dipole
elecrostatic attraction between permamnet dipoles
stronger than ldf weaker than h bond
dipoles will change their directions as that their oppositely charged ends are always facing one anotehr
h bonding
strongest imf
a type of dipole dipole interaction between molecules
form when h bonds either to N F or O with a lone pair of eletrons
the strenth is due to the small size of h in relation to the lrage electronegativbity of N O and F because electronegativity depends largely, in part, on an atom’s size
factors affecting d-d strength
increases with larger polarity (i.e a larger lectronegativity difference)
factors affecting h bond strength
increase with more lone pairs
rate the strengths of the h bonds from weakest to strongest
H to F
H to O
H to N
volatility based on imfs
how easily a subatnce becomes a gas
the wekaer imf= the more volatile as atoms move fartehr apart easier
ionic compounds and giant covalent compounds hav elow volatilities
electrical conductivity based on imfs
covalent compounds do not contain ions and thus cannot conduct electricity in any phase howver some may ionize in water and conduct electricity
ionic compounds conduct e lectrcity in the molten or aqueous state
solubility based on imfs
non poalr compounds dissolve in non polar solvents likewise for polar compounds
ionic compounds ar every soluble in water (a polar solvent) and not soluble in non polar solvents
giant covalent strcutures are non soluble in both poalr and non plar solvents due to their strong covalent bonds in teh strcuture
ways LDF is different to D-D
ldf occurs in all compounds
may occur in both atoms and molecules
are due to electron movement not e.n
transient in nature
weaker
why are smaller elements boiled at lower temps
larger atoms or molecules can ahve their electron clouds more easily deformed when exposed to external electrical dields and thus have stronger ldf attraction and higher melting and boiling points
effect of a alrger molecule on ldf
the bigger the molecule, the more electrons present,the more electrons present, and the more sites on which temporary dipoles can be induced, thus, the more polarizable the molecule is and the stronger the LDF forces are because more polarizability means stronger dipole moments formed and a greater ldf imf
