Structure and Bonding 2 - Bond Polarity and IMFs Flashcards
define electronegativity
the ability of an element to attract the pair of electrons in a covalent bond
if two atoms sharing an electron pair have different electronegative values, where do the electron pair lie, and what does this result in?
the electron pair will lie closer to the more electronegative atom, resulting in the formation of a polar covalent bond
how does electronegativity change across a period?
it increases
why does electronegativity increase across a period?
- nuclear charge increases/atomic radius decreases
- shielding remains fairly constant
- therefore bonding electrons are attracted more strongly
how does electronegativity change down a group?
it decreases
why does electronegativity decrease down a group?
- atomic radius decreases
- shielding increases
- therefore less attraction of outer shell electrons
identify in descending order the three most electronegative elements
fluorine, oxygen and nitrogen, (FON)
why are there no electronegativity values for group 8?
they have full outer shells and so do not form compounds/covalent bonds
describe the electron distribution for molecules containing identical atoms ie. H2 and O2
the shared electron pair will be in the centre of the bond because identical atoms have the same attraction (same electronegativity)
describe the electron distribution for molecules containing non-identical atoms
the shared electron pair lies closer to the more electronegative atom as it exerts a stronger attraction
molecule is said to be polar
describe and explain the bond polarity in a HCl molecule
the shared electron pair lies closer to the Cl atom as it is more electronegative and therefore exerts and stronger attraction. as a result Cl has a slight negative charge and H has a slight positive charge
which symbol is used to denote partial charges in polar molecules?
delta
define permanent dipole
when the unequal sharing of an electron pair, due to substantial differences in electronegativity between two non-identical atoms in a molecule leads to charge separation within that molecule.
why do some molecules with polar bonds not have permanent dipoles?
- due to symmetry
- causes dipoles to cancel one another out eg. CBr4
name the three types of intermolecular forces and list them from weakest to strongest
WEAKEST
van der waal
dipole:dipole
hydrogen
STRONGEST
