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An in-depth exploration of intermolecular forces (ifs), their types, properties, and examples. Ifs are electrostatic interactions between opposite charges, weaker than chemical bonds due to smaller charges and longer distances. Various types of ifs, including van der waals forces, ion-dipole forces, dipole-dipole forces, hydrogen bonding, charge-induced dipole forces, and dispersion forces. It also discusses the properties of liquids, such as surface tension, capillary action, and viscosity, and how they relate to intermolecular forces.
What you will learn
Typology: Exercises
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-^
Covalent radius
identical bonded atoms
-^
van der Waals radius
adjacent, identical (nonbonded) atoms from differentmolecules
→
The van der Waals radius of an atom is
always longer than its covalent radius
s are also called
van der Waals forces
s lead to higher
b
and
m
values
2
3
2
3
3
3
b
m
and
bonds (the
δ
of
is attracted to the
δ
of
the lone pair of
or
3
Induced dipole
through a distortion of its electron cloud by anelectric field such as a nearby charge or anotherdipole
Polarizability
cloud of a particle can be distorted (increases withincreasing the size of the electron cloud andtherefore with the molar mass of the particle) ¾
Ion-Induced Dipole
forces –
s between an ion
and a dipole it induces in a nearby particle ¾
Dipole-Induced Dipole
forces –
s between a
dipole and a dipole it induces in a nearby particle
Instantaneous dipole
an instantaneous fluctuation of the electron cloudin a particle
nearby particle and create an
induced dipole
in it
Dispersion
London
) forces –
s between an
instantaneous dipole
and an
induced dipole
in a
nearby particle
exist between
any
particles
, but
they are
the
only
type of
s for non-polar
molecules and atoms of noble gases Examples:
4
, Cl
2
, Ar, Kr, Xe … are all
non-polar
only dispersion forces are present
strength
of the dispersion forces depends on:
polarizability
(size, molar mass) of the particles
size, molar mass
dispersion forces
shape
of the particles – dispersion forces
between rod-shaped molecules are stronger comparedto spherical molecules of the same size (rod-shapesprovide more points of contact)
The boiling points of the noble gases increase downthe group as the molar mass increases
He
Ne
Ar
Kr
Xe
b^
-**
Molar mass
⇒
Dispersion forces
⇒
b
Intermolecular
Intramolecular
Adhesive forces
liquid and the walls of the capillary ¾
Cohesive forces
the liquid (
s)
The
level rises inside
a narrow glass tube
the adhesive
forces are stronger; The
Hg
level drops
inside a narrow glass tube
the
cohesive forces are stronger
η↑
with increasing the strength of the
s
η↓
with increasing the temperature (the kinetic
energy of the molecules increases relative to the IF
s of attraction between them)
3
is more viscous than
3
H-bonding
London forces
Oil and honey flow easier at higher