Ionic and Covalent Bonding in Chemistry
Ionic bonding
(metal + non-metal)
Ionic bonds form a
giant
lattice structure
Sodium chloride is an ionic compound formed by the reaction
between the metal sodium and the non-metal chlorine.
During the reaction, one electron is transferred from each
sodium atom to each chlorine atom.
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Sodium has 1 electron in its outer
shell. If it loses this electron, it will
have no partially-filled shells.
Chlorine has 7 electrons in its outer shell. If
it gains 1 electron, it will completely fill its
outer shell.
2.8.1
2.8.7
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The positive sodium ions and the negative chloride ions are strongly
attracted to each other and form an ionic bond.
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2.1
2.6
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2.8.2
2.7
Magnesium Oxide
Explain how magnesium oxide is
formed.
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Magnesium loses 2 electrons
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Oxygen gains 2 electron
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Magnesium becomes 2+
ion
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Oxygen becomes 2-
ion
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Held to together in
ionic lattice
Calcium chloride - CaCl
2
Explain how CaCl
2
is formed:
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Calcium
loses 2 electrons
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Each chlorine atom
gains 1 electron
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Two chlorine atoms needed
•
Forms
ionic bond
Covalent bonding
(non-metal + non-metal)
Simple molecules
Giant covalent structures
HYDROGEN
Another hydrogen
atom also needs one
electron to complete
its outer shell
Hydrogen atom needs
one electron to
complete its outer shell
atoms share a pair of electrons to
form a single covalent bond
A hydrogen
MOLECULE
is formed
H
WAYS TO REPRESENT THE
MOLECULE
Simple molecules
HYDROGEN CHLORIDE
Cl
Hydrogen atom also
needs one electron to
complete its outer shell
Chlorine atom needs
one electron to
complete its outer
shell
atoms share a pair of
electrons to form a single
covalent bond
WAYS TO REPRESENT THE MOLECULE
Simple molecules
AMMONIA
N
Each hydrogen
atom needs
one electron to
complete its
outer shell
Nitrogen atom needs 3
electrons to complete its
outer shell
Nitrogen can only share 3 of its 5
electrons otherwise it will exceed
the maximum of 8
A LONE PAIR REMAINS
A LONE PAIR REMAINS
WAYS TO REPRESENT
THE MOLECULE
Simple molecules
Covalent bonding - molecules
Hydrogen - H
2
(g)
Oxygen - O
2
(g)
Chlorine - Cl
2
(g)
Methane – CH
4
(g)
Hydrogen chloride
HCl (g)
Water – H
2
O (l)
Ammonia – NH
3
(g)
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In a metal the atoms LOSE SEVERAL OF THEIR OUTER
ELECTRONS which drift around between the metal ions as
FREE ELECTRONS.
•
Metals have a structure of
positive metal ions
held together by a “sea”
of electrons – causes
electrostatic attraction
•
We call these electrons
delocalized
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Ions are arranged in
layers
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Forms a
giant lattice structure
Metallic bonding
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Solid
Liquid
Gas
Melting point
Boiling point
State Symbols
(s) – solid
(l) – liquid
(g) – gas
(aq) – dissolved in water
NaOH
(aq)
→ Na
+
(aq)
+ OH
–
(aq)
High Melting point
– lots of
ENERGY
needed to break the
strong
bonds (strong electrostatic attraction)
Solubility
- Can dissolve in water which
enables the ions to
move
Conduction
- When MOLTEN or DISSOLVED IN WATER, ionic
compounds can
conduct electricity
because the ions can
carry current/charge (not electricity)
Properties of ionic compounds – giant lattices
Covalent bonding – simple molecules
Hydrogen - H
2
(g)
Oxygen - O
2
(g)
Chlorine - Cl
2
(g)
Methane – CH
4
(g)
Hydrogen chloride
HCl (g)
Water – H
2
O (l)
Ammonia – NH
3
(g)
Properties of covalent compounds
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A covalent bond is a
shared
pair of
electrons
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Substances that consist of
simple
molecules
are gases, liquids or solids
that have relatively
low melting points
and boiling points
due to
weak
intermolecular bonds
•
They
do not
conduct electricity because
the molecules
do not have an overall
electric charge
. No free electrons or
ions.
•
Molecules are linked with strong covalent bonds
•
Intermolecular forces
between
polymers are relatively strong
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Polymers are usually solid at room temperature
Polymers
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Diamond
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Diamond is made only from
carbon
atoms.
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Every carbon makes
four covalent bonds
to achieve a
full outer shell
.
•
Every carbon atom is bonded to four other carbon atoms
.
•
This means the structure keeps on growing!
•
We make a
Giant Covalent Structure
.
Giant covalent structure of diamond
Key properties –
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Diamond is very
hard.
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High melting points
– because it has strong covalent bonds
(which take a lot of energy to break)
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Graphite
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Graphite is made only from
carbon
atoms.
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Every carbon makes
3 covalent bonds
to achieve a
full outer shell
.
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Forms hexagonal rings, arranged in layers
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Weak intermolecular forces
between
the layers
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Every carbon atom is bonded to
three
other carbon atoms
Giant covalent structure of graphite
Key properties –
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Graphite is very
soft.
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Slippery
– arranged in layers
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High melting point
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Conducts electricity
–
free
electrons
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Delocalised electrons can
move
through the structure
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Ions arranged in
layers
so ions are
able to
slide
over each other
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Ions held together by
strong
electrostatic attraction
so needs a
lot of
energy
to break the bonds
Metallic bonding – giant structures
Metallic bonding - alloys
Alloys
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Mixture of metals of
different sizes.
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Distorts
the layers
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Layers can’t
slide
Besides graphite and diamond, carbon can also
form another type of giant covalent structure.
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Covalent bonding - Giant
Possible uses of Fullerenes in the future could be:
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Drug delivery
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In lubricants
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As catalysts in reactions
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To make carbon nanotubes to reinforce structures
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Structures that are 1-100nm in size, or of the order of a
few hundred
atoms
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Nanoparticles
Nanoparticles are present in sun screens
May be used to develop faster computers, lighter construction materials and new coatings
Ionic bonding involves the transfer of electrons between a metal and a non-metal to form a giant lattice structure, like in sodium chloride and lithium oxide. Covalent bonding, on the other hand, occurs between non-metals, resulting in giant covalent structures or simple molecules. Examples such as magnesium fluoride and magnesium oxide demonstrate how atoms interact to create these different types of bonds.
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Presentation Transcript
Ionic bonding (metal + non-metal) Ionic bonds form a giant lattice structure
Sodium chloride Sodium chloride Sodium chloride is an ionic compound formed by the reaction between the metal sodium and the non-metal chlorine. sodium Na chlorine Cl sodium chloride NaCl + During the reaction, one electron is transferred from each sodium atom to each chlorine atom.
Sodium chloride Sodium chloride Chlorine has 7 electrons in its outer shell. If it gains 1 electron, it will completely fill its outer shell. Sodium has 1 electron in its outer shell. If it loses this electron, it will have no partially-filled shells. - + Cl Cl Na Na [2.8]+ [2.8.8]- 2.8.1 2.8.7
Sodium chloride Sodium chloride The positive sodium ions and the negative chloride ions are strongly attracted to each other and form an ionic bond. - + Cl Na
Lithium Oxide Lithium Oxide + Li Li 2- O O [2]+ 2.1 + Li Li [2.8]2- 2.6
- Magnesium fluoride Magnesium fluoride F F 2+ [2.8]- 2.7 Mg Mg - F F [2.8]2+ 2.8.2
Magnesium Oxide Explain how magnesium oxide is formed. Magnesium loses 2 electrons Oxygen gains 2 electron Magnesium becomes 2+ ion Oxygen becomes 2- ion Held to together in ionic lattice
Calcium chloride - CaCl2 Explain how CaCl2 is formed: Calcium loses 2 electrons Each chlorine atom gains 1 electron Two chlorine atoms needed Forms ionic bond
Covalent bonding (non-metal + non-metal) Giant covalent structures Simple molecules
Simple molecules HYDROGEN WAYS TO REPRESENT THE MOLECULE H H H H Hydrogen atom needs one electron to complete its outer shell Another hydrogen atom also needs one electron to complete its outer shell H H atoms share a pair of electrons to form a single covalent bond A hydrogen MOLECULE is formed
Simple molecules HYDROGEN CHLORIDE Cl H Hydrogen atom also needs one electron to complete its outer shell Chlorine atom needs one electron to complete its outer shell WAYS TO REPRESENT THE MOLECULE atoms share a pair of electrons to form a single covalent bond H Cl H Cl
Simple molecules AMMONIA WAYS TO REPRESENT THE MOLECULE H N H H H N Each hydrogen atom needs one electron to complete its outer shell H H N H Nitrogen atom needs 3 electrons to complete its outer shell H H Nitrogen can only share 3 of its 5 electrons otherwise it will exceed the maximum of 8 A LONE PAIR REMAINS
Covalent bonding - molecules Oxygen - O2 (g) Hydrogen - H2 (g) Chlorine - Cl2 (g) Hydrogen chloride HCl (g) Methane CH4 (g) Water H2O (l) Ammonia NH3 (g)
Limitations of using models Limitations of using models doesn t show the shape shape doesn t show the
In a metal the atoms LOSE SEVERAL OF THEIR OUTER ELECTRONS which drift around between the metal ions as FREE ELECTRONS. Atoms become POSITIVE ions because they have LOST electrons Free ( delocalised ) electrons
Metallic bonding Metals have a structure of positive metal ionsheld together by a sea of electrons causes electrostatic attraction We call these electrons delocalized Ions are arranged in layers Forms a giant lattice structure
Predicting states using melting and boiling Predicting states using melting and boiling points points Substance Melting Point ( C) Boiling Point ( C) State at room temperature Water 0 99.98 Liquid Carbon Dioxide -78 -57 Gas Methane -182 -164 Gas Hydrogen -259.1 -252.8 Gas Ammonia -77.73 -33.34 Gas Boiling point Melting point Solid Liquid Gas
State Symbols (s) solid (l) liquid (g) gas (aq) dissolved in water NaOH (aq) Na+ (aq) + OH (aq)
Properties of ionic compounds giant lattices High Melting point lots of ENERGY needed to break the strong bonds (strong electrostatic attraction) Solubility - Can dissolve in water which enables the ions to move Conduction - When MOLTEN or DISSOLVED IN WATER, ionic compounds can conduct electricity because the ions can carry current/charge (not electricity)
Covalent bonding simple molecules Properties of covalent compounds Hydrogen - H2 (g) Oxygen - O2 (g) A covalent bond is a shared pair of electrons Chlorine - Cl2 (g) Methane CH4 (g) Substances that consist of simple molecules are gases, liquids or solids that have relatively low melting points and boiling points due to weak intermolecular bonds Hydrogen chloride HCl (g) Ammonia NH3 (g) Water H2O (l) They do not conduct electricity because the molecules do not have an overall electric charge. No free electrons or ions.
Polymers Molecules are linked with strong covalent bonds Intermolecular forces between polymers are relatively strong Polymers are usually solid at room temperature
Giant covalent structure of diamond Carbon structures Carbon structures - - diamond diamond Diamond Diamond is made only from carbon atoms. Every carbon makes four covalent bonds to achieve a full outer shell. Every carbon atom is bonded to four other carbon atoms. This means the structure keeps on growing! We make a Giant Covalent Structure. Key properties Diamond is very hard. High melting points because it has strong covalent bonds (which take a lot of energy to break)
