Intermolecular Forces

Question 1

Shape and structures of molecules

Answer 1

Intermolecular forces are the forces between molecules.

The shape of simple molecules can be predicted by inspection of the valence electron pairs around the central atom of the molecule.

Types: linear, V-shaped (bent), trigonal planner, tetrahedral, trigonal pyramid and octahedral.

Question 2

USEPR Theory and Covalent bonds

Answer 2

Covalent bonds: Occurs between non-metal atoms where electrons are shared between valence shells and are electrostatically attracted to both nuclei.

Theory: Valence shell electron pair repulsion.
Predicts the shape of molecules.
States that electron pairs in bonds and lame electron pairs repel each other around a central atom, forming a 3D shape.

Question 3

Electron sharing and heteroatomic molecules

Answer 3

In elemental molecules, electrons are evenly shared between atoms that make up the covalent bonds.

Heteroatomic Molecule: Electrons are not overly shared. This is caused by differences in electronegativity.

Question 4

Electronegativity

Answer 4

Measure of the tendency of an atom to attract a bonding pair of electrons within a covalent bond. The highest is fluorine.

Question 5

Polar bonds

Answer 5

The polarity of a covalent bond depends on the differences in electronegativity of each atom. A polar molecule has asymmetry of electronegativity.

Non-polar covalent: Bonding electrons are shared equally.
Polar covalent: Bonding electrons shared unequally.

Degree of polarity of molecules determines the intermolecular forces present in a substance

Question 6

VESPR

Answer 6

Provides a basis for predicting the shapes of molecules, based on their intermolecular forces which are the repulsive forces between the regions within molecules.

Allows for estimation of bond polarity which affects the strength of intermolecular forces.

Intermolecular forces are attractive forces between molecules.

Question 7

3 types of intermolecular forces

Answer 7

Dispersion very weak, dipole-dipole weak, hydrogen bonding strong.

Question 8

Dispersion

Answer 8

Exist between non-polar and polar. when more electrons are on one side than the other, it creates a temporary dipole = dipole moment also called induced dipole interaction. Their force is discounted when other types of bonding are present. Dipole points to negative, more electrons more chance of dispersion, larger atoms have greater chance of temporary dipole. You can tell if its dispersion by equal distribution of valence electrons.

Question 9

Dipole-Dipole

Answer 9

Exist between polar molecules and have a permanent dipole.
Intermolecular forces are stronger, and the packing density affects strength. Molecules must contain a polar bond and asymmetry. Negative charges are on the bottom helps to identify if its dipole if one side is unequal to the other is another indication.

Question 10

Hydrogen bonding

Answer 10

High boiling point, easier for 2 adjacent molecules can get closer together, strengthening the bond, can occur whenever there is an oxygen, charge difference over the polar covalent bond is its maximum when hydrogen is bonded.