Summarised Forces of Atrraction

Question 1

state the various forces of
attraction between
particles;

Ionic bonds, covalent
bonds, hydrogen bonds,
metallic bonds, Van der
Waals forces. (Permanent
permanent dipole;
induced-induced dipole or
temporary/instantaneous
induced dipole).

Answer 1

Intramolecular
Covalent (giant molecular and simple molecular)
ionic
metallic

Intermolecular
Hydrogen bonding
Van der Waals (permanent and temporary dipoles)

Question 2

state the relationship
between forces of
attraction and states of
matter;

Answer 2

The physical state of matter depends on the strength of the forces of attraction in and between the particles. Substances with high melting points have strong forces of attraction between their
atoms (or ions). Substances with low melting points have weak forces of attraction between their
molecules.

Question 3

relate physical properties
of matter to differences in
strength of forces of
attraction;

Variation in melting points,
boiling points and
solubilities.

Answer 3

The physical state of matter depends on the strength of the forces of attraction in and between
particles. Physical properties such as boiling point, melting point and solubility depend on the
type of forces of attraction present in compounds.

Solids
Giant structures with ionic or covalent bonds are solids with high melting points. It takes a lot of
energy to break the many strong forces between the particles. Particles are in fixed arrangement
and do not move they only vibrate.
Molecular solids have low melting points. The forces within the molecules are strong but the
forces between the molecules are fairly weak, so it does not take much energy to overcome these.

Liquids
Liquids have low melting points. The forces within the molecules are strong, but the forces
between the molecules are weak so it does not take much energy to overcome these.
Particles are close together but are more or less randomly arranged. They slide over each other.

Gases
These have very low melting points and boiling points, the forces between the molecules are
very weak so it does not take much energy to overcome these.
Particles are far apart and move randomly.

Question 4

explain the formation of
the following:

(a) ionic bonds;

(b) covalent bonds; and,

(c) metallic bonds.

Covalent bonds should be
discussed in terms of
orbital overlap which
results in the formation of
sigma (σ) and pi (π) bonds.
Metallic bonding is to be
treated as a lattice of
positive ions surrounded
by mobile electrons.
Electronegativity and
polarity of bonds should be
included.

Answer 4

This involves the transfer of electrons from a metal atom to a non-metal atom until the outer
shell of the resulting ions formed have the noble gas configuration. The metals lose electrons to
form cations, while the non-metal accepts the electrons lost from the metals and form anions.
The oppositely charged ions are attracted to each other by what is called the electrostatic force of
attraction which is a strong force that holds the ionic compound together

In metallic bonding, the metal atoms come together and donate their valence electrons to form
sea of mobile electrons which are shared among the resulting cations. Most metals exist in a
lattice of ions surrounded by a sea of delocalized electrons. Delocalized electrons are those which are not associated with any particular atom or ion. There are free to move between the
metal ions.

In terms of orbitals, a covalent bond forms when two atomic orbitals overlap.Each atom normally contributes one unpaired electron to the bond. The joined orbital is called a molecular orbital. The greater the overlap of atomic orbitals, the stronger is the
covalent bond

Question 5

describe co-ordinate
(dative covalent) bonding;
Use ‘dot-cross’ diagrams;
refer to simple systems (for
example, BF3/NH3).

Question 6

describe the origin of inter
molecular forces;

Refer to hydrogen bonding;
Van der Waals forces,
permanent dipole. Refer to
Module 3

Question 7

predict the shapes of, and
bond angles in simple
molecules and ions;
Application of the VSEPR
theory to include the
following systems: trigonal
(for example, BF3), linear
(for example, BeCl2),
tetrahedral (for example,
NH4 +, CH4), pyramidal (for
example, H3O+, CH3, and
NH3), non-linear (for
example, H2O), octahedral
(for example, SF6).

Question 8

explain the shapes and
bond angles of simple
organic compounds;

Ethane, ethene and
benzene; apply the concept
of hybridisation and
resonance. Include sp2 and
sp3 hybridisation.

Question 9

predict the shapes and
bond angles of molecules
similar to ethane; and,

Simple substituted
derivatives, for example,
dichloroethane.

Question 10

describe qualitatively the
lattice structure of
crystalline solids and their
relation to physical
properties.

Simple molecular (for
example, I2), hydrogen
bonded (for example, ice),
giant molecular (for
example, SiO2), ionic (for
example, NaCl), metallic (for
example, Cu), giant atomic
(for example, graphite and
diamond) structures