Giant Covalent & Ionic
Structures
DR FARHAD M. ALI
MARCH 2023
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Giant structures
Either covalent or ionic
 Covalent: carbon (diamond, graphite);
silicon dioxide; polymer (made from non-
metals which form giant structures)
 Ionic:
giant metallic lattice: sodium and
aluminium as examples
giant ionic lattice: ionic compounds such
sodium chloride.
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What are giant covalent structures?
• When a large number of atoms are joined by
covalent bonds, it creates a giant covalent
structure.
• A giant covalent structure has lots of covalent
bonds linking several atoms in a regular
pattern, which forms a lattice.
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Carbon atoms in diamond form a tetrahedral
arrangement. Each Carbon atom bonded to four others.
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Diamond-it is pure carbon-
It is an allotrope of carbon
• All the properties of diamond is because of
the fact that the strong covalent bonds
extended in all directions through the whole
structure of the crystal
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Graphite-it is pure carbon
It is an allotrope of carbon
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Graphite-it is pure carbon
It is an allotrope of carbon
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Graphite-it is pure carbon
It is an allotrope of carbon
• Graphite is brittle as little energy is required
to break the weak induce dipole forces but,
• it still has a very high melting point as a lot of
energy is needed to break the large number of
covalent bonds.
• Graphite has a low density because the
distance between the layers is large. As the
layers in graphite are held together by weak
intermolecular forces, the layers are far apart.
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Graphene-it is pure carbon
Also an allotrope of carbon
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Graphene-it is pure carbon
Also an allotrope of carbon
 Graphene is technically composed of carbon
atom and a covalent bond that formed a
honeycomb pattern.
 is made of a single sheet of carbon
atoms arranged in a crystal lattice (like a
honeycomb pattern).
 It is the basic building block of graphite.
 show high melting points than many other
materials
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Silicon dioxide SiO2 (also known as silica)
This is the structure of SiO2.
This has a giant structure
This is just a tiny part of a giant structure extending on all 3
dimensions.
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Silicon dioxide SiO2
• When we look at the structure we see that the
silicon bonds to 4 oxygen atoms but why do
we say SiO2?
• The Silicon atom is bonded to 4 Oxygen atoms
and each Oxygen is bonded to 2 other silicon
atoms. This leads to a ratio of 1:2
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The physical properties of silicon
dioxide
• has a high melting point (around 1700°C).
• Very strong silicon-oxygen covalent bonds have
to be broken throughout the structure before
melting occurs.
• is hard. This is due to the need to break the very
strong covalent bonds.
• doesn't conduct electricity. There aren't any
delocalised electrons. All the electrons are held
tightly between the atoms, and aren't free to
move.
• is insoluble in water and organic solvents.
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Why do giant covalent structures have
high melting points?
• These structures have high melting points due
to the covalent bonds holding the atoms
together.
• It is very difficult to break down these bonds
when they are melted and they require a large
amount of energy (i.e. a high temperature) to
break the structure.
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Are giant covalent structures soluble
in water?
• These structures are insoluble due to their
strong covalent bonds.
• Therefore, these are generally inert and so do
not react with water, making it impossible to
dissolve
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Why do giant covalent structures not
conduct electricity?
• The structures are poor electrical
conductors of electricity because they do not
have free electrons to conduct electricity
through the molecule.
• However, graphite is an exception.
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Metallic Bonding-
• Metallic bonding is a type of chemical
bonding that arises from the electrostatic
attractive force between conduction electrons
(in the form of an electron cloud of
delocalized electrons) and positively charged
metal ions
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Metallic Bonding-
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Metallic Bonding-
• Most metals have high melting and boiling points-
• Since the attraction forces between the delocalised and
positive metal ions-this need high energy to overcome this
attraction.
• Metals are good conductors for heat and electricity-
• Since the mobile electrons can move throgh the structure,
carrying electricity.
• They are malleable: easily bent and shaped
• ductile: streched into wires
• Atoms of metal arranged in layers-when a forc is applied,
the layers can slid over each other-forming new bonds this
will leave the metal with a different shape.
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