Chapter 11 Flashcards
intermolecular forces are generally much ____ than bonding forces
weaker
Why are intermolecular forces much weaker than bonding forces?
because bonding forces are a result of large charges (protons and electrons) interacting at close distances where as intermolecular forces are a result of smaller charges interacting at greater distances (coulumbs law)
What happens when an ion approaches a non-polar atom or molecule?
the negative electron cloud of the nonpolar atom or molecule distorts and the ion induces a small dipole in it
define ion-induced dipole forces
a intermolecular force between ions and a nonpolar molecule
what is the magnitude of ion-induced dipole forces depend on?
the charge of the ion and how easily the electrons in the atom or molecule can move or polarize in response to the presence of the ion
what is the magnitude of the polarizibility of an atom or molecule dependent on (in part)?
the size (or volume) of the electron cloud
a larger electron cloud results in a ______ dispersion force because….
greater
the electrons are held less tightly by the nucleus and are therefore easier to polarize
define dispersion force (sometimes called the London force)
an intermolecular force exhibited by all atoms and molecules that results from fluctuations in the electron distribution in the absence of an ion
what are dispersion forces a result of?
the fluctuations in the electron distribution within atoms or molecules in the absence of an ion
what is a temporary or instantaneous dipole?
a temporary dipole caused by electrons being unevenly separated
how does an instantaneous dipole affect the atoms around it?
it can induce an instantaneous dipole in the other atoms because of the attraction of the electrons to the positive side of the atom. they then all organize themselves positive to negative
what is the magnitude of an instantaneous dipole’s dispersion determined by?
how easily the electrons in the atom or molecule can mover or polarize in response to an instantaneous dipole, which partly depends on the size of the electron cloud.
for noble gases, as the number of electrons increases, the volume of the electron cloud _____, and the _____ dispersion forces result in an ______ boiling points
increase
greater
increasing
does the number of electrons determine the magnitude of the dispersion force? why?
not alone. shape also affects the dispersion forces (and an atoms boiling point)
atoms with larger areas for interaction will have a ______ dispersion force than atoms with smaller areas for interaction
greater
define dipole-dipole force
an intermolecular force exhibited by polar molecules that result from the uneven charge distribution
what type of molecules have permanent dipoles?
polar molecules
define permanent dipole
a permanent separation of charge; a molecule with a permanent dipole always has a slightly negative charge at one end and slightly positive charge at the other
the attraction of the postive end of one permanent dipole to the negative end of another permanent dipole is an example of which force?
dipole-dipole force
due to dipole-dipole forces polar molecules have a ______ melting point than non polar molecules with a similar number of electrons or of similar size
higher
do all molecules have dispersion forces?
yes
define miscibility
the ability to mix without separating into two phases
in general polar liquids _____ miscible with other polar liquids and _____ miscible with non polar liquids
are
are not
define hydrogen bonding
a strong type of intermolecular bonding that occurs between polar molecules that contain hydrogen atoms bonded directly to small electronegative atoms (like O, F, or N)
