Bonding, Structure and the Properties of Matter

Question 1

What is ionic bonding?

Answer 1

Ionic bonding is the electrostatic attraction between positive and negative ions.
It is a relatively strong attraction.

Question 2

How are ionic compounds
held together?

Answer 2

● They are held together in a giant lattice.
● It’s a regular structure that extends in all directions in a substance.
● Electrostatic attraction between positive and negative ions holds
the structure together.

Question 3

State properties of ionic
substances

Answer 3

● High melting and boiling point (strong electrostatic forces between
oppositely charged ions)
● Do not conduct electricity when solid (ions in fixed positions).
● Conduct when molten or dissolved in water - ions are free to move.

Question 4

Give 5 examples of positive ions and
5 examples of negative ions.
What is important when working out
a formula of an ionic compound?

Answer 4

E.g. Positive: Na+
, Mg2+, Al3+, Ca2+, Rb+

E.g. Negative: Cl−, Br−
, SO42−, NO3
−
, OH−
(chloride, bromide, sulfate, nitrate,
hydroxide).
Ionic compounds are electrically neutral, i.e. positive and negative charges balance each other.

Question 5

How are ionic compounds
formed? Explain in terms of
MgO case.

Answer 5

Reaction of a metal with a non-metal.
Electron transfer occurs - metal gives away its outer shell electrons to
non-metal.
Mg is in Group II, so has 2 available outer shell electrons.
O is in Group VI, so can accept 2 electrons to get a full outer shell
configuration.
Mg becomes Mg2+ and O becomes O2− (oxide).

Question 6

What is a covalent bond?

Answer 6

Covalent bond is a shared pair of electrons between two atoms.

Question 7

Describe the structure and
properties of simple molecular
covalent substances

Answer 7

Do not conduct electricity (no ions)
- Small molecules
- Weak intermolecular forces, therefore:
- Low melting and boiling points

Question 8

How do intermolecular forces
change as the mass/size of the
molecule increases?

Answer 8

They increase. That causes melting/boiling points to increase as well (more
energy needed to overcome these forces).

Question 9

What are polymers? What are
thermosoftening polymers?

Answer 9

Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by
covalent bonds.
Thermosoftening polymers - special type of polymers; they melt/soften when
heated. There are no bonds between polymer chains. Strong intermolecular forces
ensure that the structure is solid at room temperature. These forces are overcome
with heating - polymer melts.

Question 10

What are giant covalent
substances? Give examples

Answer 10

Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points – strong covalent bonds.
- Mostly don’t conduct electricity (no delocalised e−
)
- Diamond, graphite, silicon dioxide.

Question 11

Describe and explain the
properties of allotropes of carbon.

Answer 11

Diamond
– four, strong covalent bonds for each carbon atom
– very hard (Strong bonds)
– very high melting point (strong bonds)
– does not conduct (no delocalised electrons)
Graphite
– three covalent bonds for each carbon atom
– layers of hexagonal rings
– high melting point
– layers free to slide as weak intermolecular forces
between layers; soft, can be used as a lubricant
– conduct thermal and electricity due to one delocalised
electron per each carbon atom
Fullerenes
– hollow shaped molecules
– based on hexagonal rings but may have
5/7-carbon rings
– C60 has spherical shape, simple
molecular structure (Buckminsterfullerene)
Nanotubes
– cylindrical fullerene with high length to
diameter ratio
- High tensile strength (strong bonds)
- Conductivity (deloc. electrons)
Graphene - a single layer of graphite.

Question 12

What is metallic bonding?

Answer 12

Forces of attraction between delocalised electrons and nuclei of metal
ions.

Question 13

Describe properties of
metals

Answer 13

High melting/boiling points (strong forces of attraction)
- Good conductors of heat and electricity (delocalised electrons)
- Malleable, soft (layers of atoms can slide over each other whilst maintaining
the attraction forces)

Question 14

What are alloys? Why are
they harder than pure
metals?

Answer 14

Alloys:
- mixtures of metal with other elements, usually metals
- different sizes of atoms distorts the layers, so they can’t slide over each other,
therefore alloys are harder than pure metals

Question 15

What are the limitations of
the simple model?
Higher tier only

Answer 15

There are no forces between spheres and atoms, molecules and ions are solid
spheres – this is not true

Question 16

What does the amount of energy
needed to change state from solid
to liquid or liquid to gas depend
on?

Answer 16

The strength of the forces between the particles of the substance. The
nature of the particles involved depends on the type of bonding and the
structure of the substance. The stronger the forces between the particles
the higher the melting point and boiling point of the substance

Question 17

A pure substance will melt
or boil at…? What about the
mixture?

Answer 17

A fixed temperature.
A mixture will melt over a range of temperatures.

Question 18

What are the three states of
matter?

Answer 18

Solid, liquid and gas

Question 19

What is nanoscience?

Answer 19

Science that studies particles that are 1 - 100nm in size

Question 20

State the uses of
nanoparticles

Answer 20

Medicine (drug delivery systems)
- Electronics
- Deodorants
- Sun creams (better skin coverage and more effective protection
against cell damage)

Question 21

What are fine and coarse
particles?

Answer 21

Fine particles (soot), 100-2500 nm diameter
- Coarse particles (dust), 2500-105
nm diameter

Question 22

Why do nanoparticles have
different properties to those for
the same materials in bulk?

Answer 22

High surface area to volume ratio