3.1 Intermolecular and Interparticle Forces

Intermolecular forces, IMF, are the attractions BETWEEN _____ that hold them together.

atoms, ions or molecules

How many types of intermolecular forces are there?

6

Intermolecular forces differ in the:

arrangement of the electrons

Intermolecular forces explain why;

Substances made from the same elements are of different states

To determine which type of IMF a substance will exhibit you need to look at the:

types of atoms that are present in the sample.

To determine which type of IMF a substance will exhibit you have to identify:

the types of atoms in the sample as either a metal or a nonmetal

Intermolecular forces from weakest to strongest:

London dispersion, dipole dipole, hydrogen bonding, ionic, metallic, covalent network

Van der Waal’s forces include:

London dispersion, dipole-dipole, hydrogen bonding

Hydrogen bonding is a strong type of:

dipole-dipole bond

Strength of ionic and metallic bonds:

Strong

Are ionic or metallic bonds stronger?

Both strong, difficult to compare

Which substances have London dispersion forces?

All substances

London dispersion forces are the only force in:

nonpolar molecules or single nonmetal atoms

Ne, H2, CO2 have what force?

London dispersion

What substances have dipole-dipole forces?

Polar molecules and asymmetrical molecules with only non-metals

HCl, CH2O, CH3Cl have what force?

Dipole dipole

Hydrogen bonding occurs in:

polar molecules that have hydrogen directly bonded to N, O or F.

HF, H2O, CH3OH have what force?

Hydrogen bonding

Ionic bonds occur in substances with:

metal bonded to nonmetal

NaCl, KBr, MgO have what force?

Ionic

Metallic forces occur in:

Only metal atoms

Au, Al, ZnCu have what force?

Metallic

C(diamond), C(graphite), C60, SiO2, SiC have what force?

Covalent network

London dispersion forces are caused by the:

motion of electrons within an atom or molecule

As the electrons move around with the atom there is a chance that they are:

unequally distributed

When electrons are unequally distributed within an atom it causes the atom or molecule to have a:

“temporary dipole”

Why does an atom or molecule have a temporary dipole when electrons are unequally distributed within an atom?

due to there being an excess of negative charge (partially negative, δ-) in one place and an area that is deficient in electrons and therefore is more positive (partially positive, δ+).

The temporary dipole in one atom or molecule causes:

the neighboring atoms/molecules to change

What change does the temporary dipole in one atom or molecule cause in the neighboring atoms/molecules?

the negative end of the temporary dipole repels electrons while the positive end of the dipole attracts electrons.

When the neighboring species’ electrons move due the negative end of a temporary dipole repelling electrons and the positive end of a dipole attracting electrons this forms an:

“induced dipole”

The induced dipole is ______ attracted to the first atom/molecule.

electrostatically

An induced dipole is long-lasting / short-lived

short-lived

What happens to an induced dipole over time?

Return to being evenly distributed

Is London Dispersion force weak or strong?

Weak

Why is London Dispersion Force weak?

Short-lived and will return to being evenly distributed

The ability of an atom to form a temporary or induced dipole

Polarizability

London dispersion forces are stronger when:

an atom or molecule has more electrons

London dispersion forces being stronger when an atom or molecule has more electrons is shown in the:

halogens

How do the halogens show that London Dispersion forces are stronger when an atom or molecule has more electrons?

Moving down the periodic table, halogens change in state from being liquid to solid

Relationship between polarizability and size of molecules and number of electrons

Directly correlated

Factors that increase strength of London dispersion force:

Number of electrons and shape of molecule and presence of pi bonding

How does shape of molecule affect strength of London Dispersion force?

Long, thin molecules have more surface area and are more polarizable while short, round molecules have less surface area and are less polarizable.

Polarizability increases as the strength of London dispersion forces increases/decreases

Increases

Pi bonding means the presence of:

Double or triple bonds

Dipole-dipole interactions occur between molecules that:

have a permanent dipole

Why do some molecules have a permanent dipole?

They are polar molecules

Molecules are polar when:

their electron distribution is asymmetrical

Dipole-dipole forces vs London Dispersion forces:

Permanent and greater attractions

Dipoles can be measured by:

the dipole moment of the molecule

Dipole-dipole interactions are stronger when the substance involved is:

more polar

A substance being more polar means that electrons are:

more unequally distributed

What do we consider when trying to determine strength of dipole-dipole interactions?

electronegativity values of the elements involved

Hydrogen bonding occurs in molecules that contain:

H-N, H-O or H-F bonds.

Why does hydrogen bonding form between H-N, H-O or H-F bonds?

difference in electronegativity is so large that a large bond dipole forms

Which is partially positive and negative in hydrogen bonding?

Hydrogen is partially positive and oxygen, fluorine, and nitrogen are partially negative

Can the partially positive hydrogen bind to a partially negative nitrogen, fluorine, or oxygen within the same molecule to form a hydrogen bond?

Yes

When can the partially positive hydrogen bind to a partially negative nitrogen, fluorine, or oxygen within the same molecule to form a hydrogen bond?

When molecule is large

Where can partially negative come from to form hydrogen bonds?

N, O, F atom or the lone pair on the N,O, F atom

Rank the strength of the hydrogen bonds in H-F, H-O, and H-N

H-F > H-O > H-N

H-F > H-O > H-N is due to:

Changes in electronegativity

Strength of hydrogen bonding increases/decreases when there are multiple sites for hydrogen bonding

increases

The strength of London dispersion forces in nonpolar molecules increases with the:

polarizability of the molecules

The strength of dipole-dipole force depends on:

magnitudes of the dipoles and their relative orientation

Interactions between polar molecules are typically greater/less than those between nonpolar molecules of comparable size

greater

Why are interactions between polar molecules are typically greater than those between nonpolar molecules of comparable size?

These interactions act in addition to London dispersion forces.

Name of interaction between two polar substances: (Except London dispersion)

Dipole dipole

Name of interaction between a nonpolar and a polar substance: (Except London dispersion)

Dipole-Induced dipole

The strength of Dipole-induced dipole forces increases with:

the magnitude of the dipole of the polar molecule and with the polarizability of the nonpolar molecule.

nonpolar substance: (Except London dispersion)

Ion-induced dipole

Strength of ion-induced dipole increases with:

larger charged ions, smaller ion size and more polarizable molecules

Name of interaction between an ion and a polar substance: (Except London dispersion)

Ion-dipole

Strength of ion-dipole force vs dipole-dipole force:

Higher

The strength of ion-dipole force increases with:

larger charged ions, smaller ion size and more polar molecules.

What determines the shape of large biological molecules?

Covalent bonds, intermolecular and intramolecular forces

Which bonding occurs in many biological molecules?

Hydrogen bonding

Are ionic, metallic, and covalent network intermolecular forces?

No

Ionic interactions occur betweenIo:

metal and nonmetal atoms

Ionic interactions occur when:

Metal and nonmetal atoms lose or gain electrons to form ions

Ionic interactions are a _______ attraction

Coulombic or electrostatic

The ionic bonds are stronger when:

the charges are larger and the ions are smaller

Ionic bonds being stronger when the charges are larger and the ions are smaller is explained by:

Coulomb’s Law

Coulomb’s law:

Metallic bonding occurs between:

metal atoms

Metallic bonding can be for:

one type of metal or different types of metal

Mixture of different types of metals is called:

Alloy

One type of metal is known as a:

pure substance

Metallic attractions are due to:

Multiple metallic cations being attracted to a delocalized sea of valence electrons.

Metallic attractions are stronger when:

there are smaller metallic cations and when there are more valence elections.

Covalent network occurs between:

carbon atoms, silicon atoms, carbon with oxygen or silicon, and silicon with oxygen.

Covalent network attraction is due to:

multiple covalent bonds forming a large macromolecule.

Covalent network is stronger when:

more covalent bonds are formed

When intermolecular force increases, Boiling/Melting/Freezing etc. Point increases/decreases

Increases

When intermolecular force increases, Enthalpy of fusion/vaporization etc. increases/decreases

Increases

When intermolecular force increases, vapor pressure increases/decreases

Decreases

When intermolecular force increases, viscosity increases/decreases

Increases

When intermolecular force increases, surface tension increases/decreases

Increases

When intermolecular force increases, solubility increases/decreases

Increases

Solubility decreasing as a result of increasing intermolecular force depends on:

polarity of the solvent and solute

When intermolecular force increases, lattice energy increases/decreases

Increases