Group 1 – Graphite Graphite
1. Definition of “allotrope”
Different physical forms (and structural modifications) of the same element.
2. Explain the structure of the substance you are researching.
a.
What does it look like?
3. Explain the bonding in the substance.
a.
How are the atoms bonded to each other?
Has a layered, planar structure. In each layer, the carbon atoms are arranged in a hexagonal
lattice.
4. Relate the bonding and structure to the physical and chemical properties of the
substance.
a.
How do the bonds and forces between the atoms explain its overall structure?
The sp2 hybridization of carbon results in planar structures. Layers are only weakly linked to the
next layer.
b.
1.
2.
3.
4.
What properties are characteristic of this substance?
Soft and slippery
Brittle
Electrical conductor
Insoluble in water
5. Very high melting point
c. How does the bonding and structure contribute to its properties.
1. Covalent bonds hold structure together in 2 dimensions, hence layers are free to slide
easily over one another.
2. Bonds are directional within a layer and stress across the layer will break them.
3. 3 of the valence electrons are used in sigma bonding.
a.
Makes giant molecular pi orbitals that allow electrons to move freely.
4. There are only weak attractions between carbon atoms and water molecules, but carbon
atoms are bonded tightly to one another.
5. Covalent bonds hold layers together, therefore high amounts of energy are needed to pull
it apart.
5. List a few practical uses of the substance in chemistry and in everyday life.
In chemistry:
- Used to make crucibles (Resistant to chemicals, high melting point, good
conductor of heat)
- Used to make electrodes (presence of free electrons = good conductor of
electricity)
- Used in nuclear reactor to control the speed of the nuclear fission reaction.
(ability to absorb fast-moving neutrons)
In everyday life:
- Lead pencil lead (of different hardness)
- Dry lubricant in machine parts (due to slippery nature)
- Used as a conductor of electricity in homes
- Various commercial structures made from carbon fiber
graphite composites (ex. fishing rods, golf club shafts, bicycle frames, sports car body panels,
pool cue sticks, etc)
- Steel hardener
- Brake linings
Group 2 – Diamond ALLOTROPES – Different forms of a chemical element that exist in the same state (solid, liquid or gas) but have different properties due to the different arrangement of their atoms Allotropes of Carbon: Graphite, Charcoal and Diamond Diamond is a giant molecular structure (lattice) where each carbon atom is covalently bonded to four other carbon atoms. As each carbon has four single bonds it is sp^3 hybridized and has tetrahedral bond angles of 109 degrees. It’s Properties: •
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Shiny Colourless and clear (transparent) Hard and brittle o Due to lattice structure – atoms ‘locked’ in place High melting point Insoluble in water Not very conduct o Due to lattice structure Not reactive – all the atoms are bonded to each other Absorbs heat Practical uses in chemistry and in everyday life: •
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Can be used for cutting tools and drill bits Grinding, cutting, drilling, polishing Coating for machine parts – due to the fact that it draws heat Draw heat away from electronic components Group 3 – Graphene Group 4 – C60 Fullerene Define Allotropes:
Different structural modifications of an element where the atoms of the elements are bonded
together in a different matter
Structure:
1. What does it look like?
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A truncated icosahedron
Resembles the shape of a soccer ball (twenty hexagons and twelve pentagons)
Explain the bonding in the substance:
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Covalently bonded
A carbon atom at the vertices at each polygon and a bond along each polygon edge
Forms exohedral complexes and endohedral complexes( atoms may bond to C60 by
attaching to the outside of its cage or by being trapped inside the cage)
Relate the bonding and structure to the physical and chemical properties of the
substance:
How do the bonds and forces between the atoms explain its overall structure?
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The carbon atoms on each vertices of each polygon forms a bond between the
polygon’s edge and also form bonds to other carbon atoms in the molecule, creating a
ball-like shape.
What properties are characteristics of this substance?
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extremely high melting point (~600 degrees celsius)
soft and slippery
brittle
electrical insulator
insoluble in water
How does the bonding structure contribute to its properties?
● soft and slippery because there are few covalent bonds holding the molecules together
but only weak Vander Waals forces between molecules.
● brittle because of weak crystals typical of covalent substances
● electrical insulator because no movement of electrons available from one molecule to
the next.
● insoluable in water because there are only very weak Van der Waal's attractions
between the carbon atoms and the water molecules whereas the carbon atoms are
bonded very tightly to one another in the molecules.
List practical uses in chemistry and in everyday life
● currently under study for potential medicinal use (eg. binding specific antibiotics to the
structure to target resistant bacteria and even certain types of cancer cells, such as
melanoma.)
● photo-detectors and photo-voltaics
● polymer electronics
● antioxidants and biopharmaceuticals
Group 5 – Quartz Allotropes: Different structural modifications of an element the atoms of the element are
bonded together in a different manner.The property of some chemical elements to exist in
two or more different forms in the same physical state.
Quartz
Quartz belongs to the trigonal crystal system.The ideal crystal shape is a six-sided
prism terminating with six-sided pyramids at each end
Structure:
• Is held together by a continuous three dimensional work of covalent bonds the
electron are constrained in pairs to a region on a line between the centers of pairs of
atoms
Properties:
• Solid that is extremely hard, It has a hardness of 7 on the mohs scale, makes it very
durable
• has a very high melting point
• chemically inert in contact with most substances
• will not conduct electricity either as a solid or molten, has electrical properties and
heat resistant, valuable in electronic products
Uses:
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useful as a gemstone(colourful), in the making of glass, as an abrasive, as a foundry
sand, used in petroleum in a process called hydraulic fracturing