Transcript GCSE Additional Science Chapter 7 Bonding, Structure and Chemical Properties CHEMISTRY 2 The Periodic Table Non Metals He Li Be B C N O F Ne Na M g Al GCSE Additional Science Chapter 7 H P S Cl Ar K Ca Sc Ti V Cr M n Fe Co Ni Cu Zn Ga Ge As Se Br Kr Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Rb Sr Y Zr Nb M o Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Metals Comparing the properties of metals and nonmetals GCSE.

GCSE Additional Science
Chapter 7
Bonding, Structure and
Chemical Properties
CHEMISTRY 2
The Periodic Table
Non Metals
He
1
2
Li
Be
B
C
N
O
F
Ne
3
4
5
6
7
8
9
10
Na
M
g
Al
4
11
GCSE Additional Science
Chapter 7
H
13
P
S
Cl
Ar
15
16
17
18
12
K
Ca
Sc
Ti
V
Cr
19
20
21
22
23
24
M
n
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
26
27
28
29
30
31
32
33
34
35
36
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
43
44
45
46
47
48
49
50
51
52
53
54
25
Rb
Sr
Y
Zr
Nb
37
38
39
40
41
M
o
42
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Metals
Comparing the properties of metals and nonmetals
GCSE Additional Science
Chapter 7
Metals
Non-Metals
Good conductors of electricity
Poor conductors of electricity
Good heat conductors
Poor heat conductors
Malleable (can be moulded into
shape)
Non-malleable (brittle in their
solid form)
Ductile (can be pulled into
wires)
Non-ductile
Shiny (when freshly cut)
Not usually shiny
Many have high melting points
Low melting point
Many have high boiling points
Low boiling point
Metals
The key to understanding a metal’s
properties lies in its structure
positive ions
A metal structure is an ordered
pattern of positive ions in a ‘sea’ of
negative electrons.
free electrons
Ductility
GCSE Additional Science
Chapter 7
Electrical
Conductors
Connecting the
sides to a battery
makes the electrons
move from the
negative side
towards the positive
– this is the flow of
current.
Explaining the
properties of
METALS
Electrons act as a type of
lubricant between the
layers of ions. This
explains why it’s possible
to pull metals to form wires.
Melting Point
The strength of metallic bonds depends on the
number of outer electrons in the atoms (the more
outer electrons there are , the higher the melting
point).
Alloys
Stainless steel is an example of an alloy
used to make saucepans and cutlery.
GCSE Additional Science
Chapter 7
Some modern alloys can recover their
shape after bending. These are used in
frames for glasses. They are a type of
‘smart material’ called shape-memory alloy.
Metallic Glass
As mentioned previously, most solids have a structure that shows a
regular pattern but it’s possible to form metals that show less of a
pattern – these are the metallic glasses.
Metallic glasses are three times as
strong as steel and ten times more
flexible, making them ideal for use as
golf club-heads.
BONDING
Ionic Structures
Sodium chloride is formed when atoms of sodium bond with atoms of chlorine.
Cl-
GCSE Additional Science
Chapter 7
Na+
+) [2.8]
Sodium atom
ion (Na
(Na)
[2.8.1]
-) [2.8.8]
Chlorine ion
Chloride
atom
(Cl(Cl)
[2.8.7]
Both atoms are trying to achieve a full set of outer electrons. They can do this if the
sodium atom gives its outer electron to the chlorine atom.
We now have a sodium ion Na+, and a chloride ion Cl-.
BONDING
Ionic Structures
GCSE Additional Science
Chapter 7
Na+
Cl-
Sodium ion (Na+) [2.8.]
Sodium chloride (salt)
Chloride ion (Cl-) [2.8.8]
BONDING
Ionic Structures
So there are two types of ion:1)
Positive ion (cation) – the atom has lost an electron
or electrons.
2)
Negative ion (anion) – the atom has gained
electron(s).
The ions attract and the attraction is ionic bonding.
GCSE Additional Science
Chapter 7
The oppositely charged ions attract each other. They cluster around each other
(six Cl- around each Na+ and vice versa) to make an ionic giant structure.
Six Chloride
ions cluster
around one
Sodium ion
Molecular structure of Sodium Chloride
(Click molecule to show animation)
Six Sodium
ions cluster
around one
Chloride ion
Properties of Ionic Compounds
PROPERTY
GCSE Additional Science
Chapter 7
High melting point
DUE TO
Strong electrostatic forces of
attraction between the ions. A lot
of energy is needed to break them.
Solid ionic compounds do not The ions are held in fixed
positions, and are not free to
conduct electricity.
move.
Molten ionic compounds Melting has separated the ions so
that they can move past each
conduct electricity.
other.
BONDING
Covalent Bonding
Non-metal atoms bond with each other by sharing outer shell electrons.
GCSE Additional Science
Chapter 7
This is called COVALENT BONDING.
Covalent bonding can produce:
•Small molecules of elements, e.g. H2
•Small molecules of compounds, e.g. HCl
•Giant molecules of elements, e.g. diamond and graphite
•Giant molecules of compounds, e.g. SiO2
BONDING
Covalent molecules
Some elements form covalent compounds. This happens as atoms share electrons.
GCSE Additional Science
Chapter 7
H
Cl
Hydrogen atom (H) [1]
Chlorine atom (Cl) [2.8.7]
Molecule of hydrogen chloride (HCl)
Hydrogen has the electron pattern of helium, and chlorine has the electron pattern
of argon.
This is written as H-Cl, where the ‘-’ represents a covalent bond (pair of
shared electrons).
Properties of molecular covalent compounds
GCSE Additional Science
Chapter 7
Melting points
Low
(attraction between molecules is weak)
Physical state at room
temperature
Gases or liquids with low boiling points or
solids with low melting points
(weak forces of attraction between molecules)
Electrical conductivity
Do not conduct electricity
(the molecules have no charge)
Solubility in water
Most are insoluble in water
An exercise to recognise atomic or covalent
bonds.
(Only the outer shell is shown in the diagrams)
H
Ca2+ F2ionic
H
O
covalent
H
covalent
Cl
GCSE Additional Science
Chapter 7
H
Mg2+ Cl-2
ionic
Cl
covalent
O
H
Cu
N
H
H
covalent
Show the answers
Cu2+
O2ionic
Giant Covalent Structures
Comparing the properties of graphite and diamond
Some covalent molecules exist as giant covalent structures. These have a high
melting point because all the atoms are held by strong covalent bonds. Graphite
and diamond are examples of giant covalent structures made up of a collection
of carbon atoms only.
GCSE Additional Science
Chapter 7
PROPERTY
Appearance
Hardness
Conductivity
Melting point
Diamond
Graphite
Transparent crystals
Grey/ black shiny solid
Incredibly hard – used for cutting
glass and in drill bits for drilling
through rocks in the oil industry.
Very soft – used as a lubricant.
Also used to make pencils.
Electrical insulator
A non-metal that conducts
electricity. Used for making
electrodes.
Very high – over 3500°C.
Very high – over 3600°C.
An explanation of the properties of diamond and
graphite
GCSE Additional Science
Chapter 7
Diamond
Every atom is bonded to 4 other
atoms. Every outer electron has
its role to play in the covalent
bonding that happens here. The
result is a very rigid structure. As
there are no free electrons, it
doesn’t conduct electricity and it’s
a good conductor of heat.
Graphite
Graphite has layers formed from
hexagonal rings – these layers can slide
over each other, and this is why it is used
as a lubricant.
Every carbon atom bonds strongly to other
carbon atoms by three covalent bonds.
The fourth outer electron in each atom is
free to move, and this is what makes
graphite a good conductor.
The future, and other forms of carbon
Whilst experimenting with Fullerene C60, it
was found that other structures of carbon
could be formed. One of them is seen
below:
GCSE Additional Science
Chapter 7
Fullerene C60
The carbon atoms are bonded
covalently into a football shape.
Carbon Nanotube
The nanotube is like rolled graphite.
1) It conducts electricity
2) It’s very small – 10,000 times thinner
than a human hair
Nanotube
3) Crystals can be grown inside it
Human
hair
4) They may solve the problem of how
to produce smaller circuits, where
they might replace wires.