Fabrication and Physical Properties of Single-Crystalline ...
IB Chemistry on Allotrope, Alloy, Graphene and crystalline structure
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Transcript of IB Chemistry on Allotrope, Alloy, Graphene and crystalline structure
Allotropes of Carbon Element exist in different form/physical state
Diamond Fullerene, C60
• Carbon- sp2 hybridization • Bonded in geodesic shape• 60 carbon in spherical - 20 hexagon/ 12 pentagon• 1 π electron free to delocalized. • Surface is not planar, but sphere• Electrons NOT able to flow easily.
Graphene
• Carbon- sp2 hybridization• Carbon bond to 3 others form hexagon (120) • Exist chicken wire/honeycomb- 1 layer
Click here to viewClick here to view Click here to view
• Carbon- sp3 hybridization• Bonded tetrahedrally• Strong hard covalent network
• Carbon- sp2 hybridization• Bonded Trigonal planar (layers)• Giant covalent structure (2D)• Strong covalent network within layers• Weak Van Der Waals force bet layers
Giant covalent structure (3D)
Giant covalent structure (2D)
Molecular structure
✓
✓✓
Giant covalent structure (2D) ✓
Uses of graphene
Graphite
Bond to 4 C atoms
Bond to 3 C atoms
Bond to 3 C atoms
…
Allotropes of Carbon Element exist in different form/physical state
Diamond Fullerene, C60GrapheneGraphite
Electrical conductivity
Special property
Electrical conductivity Electrical conductivity Electrical conductivity
Special property
Good
- Within layer, C sp2 hybridized- ONE free delocalized π electron
Very Good
- Within layer, C sp2 hybridized- ONE free delocalized π electron
moving across the layer easily
Poor
- C sp3 hybridized- No free moving electron
Semiconductor ✓✗
- Surface sphere, not planar- Electrons CANNOT flow easily.- Lower electron mobility
- Soft, layer slide across each other
- Hardest substance- Jewellery
Special property
graphite lubricant electrode
Lightest/strongest material
replacing silicon in photovoltaic cell
Drug delivery Transistor/ElectronicTransparent conducting
electrode
Click here uses grapheneDrug in graphene
Allotropes of Carbon Element exist in different form/physical state
Fullerene, C60Graphene
Click here to view touch screen
Electron in hexagonal rings do not
delocalized over whole molecule.
6:6 bond shorter than 6:5
6:5 bond bet hexagon and pentagon
Macroscopic properties• High tensile strength• High electrical /heat conductivity• High ductility and chemical inactivity
60 carbon in spherical((20 hexagon/12 pentagon)
Potential medicinal use• Trap/bind drug inside/outside cage• Target cancer cells
Drug inside Drug bind outside
• sp2 hybridization• Exist as 2D/chicken wire/honeycomb• Stronger than diamond, x200 stronger steel• Conductive than copper• Flexible/Transparent/lighter than rubber• Solar cell and batteries
Graphene touch screen and photovoltaic cell
Click here for application of graphene
Single sheet conductor Rool into conductive nanotubes
Electrical contact
photovoltaic cell
Lightest and strongest replacing silicon in photovoltaic cell
6:6 bond length bet two hexagon
Double bondSingle bond
Uses of Carbon Allotropes
• Conduct current/heat very well• Conduct current at speed of light • Electron delocalized above/below plane• High electron mobility
Click here discovery graphene Click here CNT Click here to view
sp2 hybridization
graphene
rool into rool into
Carbon Nanotube (CNT)
CNT- fullerene family of carbon allotropes. Hollow cylindrical moleculeRolling single or multiple layers of graphene sheet. Single-wall SWNT/ multi-wall MWCNTHigh tensile, stable, unreactive
Single wall Nanotube (SWNT) Multi wall Nanotubes (MWNT)
Click here TEDtalk graphene
1 layer thick
Uses of CNT
Strong tubes as
space elevatorFilter off salt
(desalination)
Drug delivery to body Attachment drug
therapeutics
Metallic Bonding
MetalsMetallic bonding
Electrostatic forces attraction - bet lattice of positive ions with
delocalized electron
Metallic elements- Cu, Na, K, Cu
Lattice of positive ions with sea of free electrons
Metallic Bonding
Metallic Property
Electrical conductivity Malleability/Ductile High melting point
Delocalized free moving electron carry charge/heat
heat flow
High Temp Low Temp
Thermal conductivity
electron flow
✓
Form sheet by hammering
Ductile -stretch into wires
Bend and shaped
Atom able to roll/slide to new position
without breaking metallic bond
Strong Electrostatic force attraction - between lattice of positive ions with
delocalized electron
Melting Point • Temp when solid turn to liquid (temp remain constant)• Energy absorb to overcome forces attraction bet molecule
Factors affecting melting point for metals
• Melting point across Period 2/3• Melting point down Gp 1
Gp 1
Period 2/3
Metallic Bonding
Melting Point metals
period 2
period 3
Li
Be
B
C
N O F Ne
Na
MgAI
Si
P SCI
Melting point across Period 2 and 3
Electrostatic forces attraction - bet lattice of positive ions with
delocalized electron
Melting point across Period 2 and 3
Size of atom decrease ↓ Number delocalized electron increase ↑
Electrostatic forces attractionINCREASES ↑
Melting point INCREASE ↑ ✓
Electrostatic force attraction
Metallic Bonding
Metalic Bonding INCREASE ↑
Melting Point
Factors affecting melting point for metals
Gp 1
Period 2/3
Metallic Bonding
Melting Point metals
Melting point down Group 1
Electrostatic forces attraction - bet lattice of positive ions with
delocalized electron
Melting point down Gp 1
Size of atom increase ↑ Valence electron furtheraway from positive nucleus
Electrostatic forces attractionDECREASES ↓
Melting pointDECREASE ↓ ✓
Electrostatic force attraction
Metallic Bonding
Size of atom increases
Metallic BondingDECREASE ↓
• Temp when solid turn to liquid (temp remain constant)• Energy absorb to overcome forces attraction bet molecule
• Melting point across Period 2/3• Melting point down Gp 1
Melting Point
Gp 1
Period 2/3
Metallic Bonding
Melting Point metals
Electrostatic forces attraction - bet lattice of positive ions with
delocalized electron
✓
Electrostatic force attractionMetallic Bonding
Number delocalized electrons
Factors affecting Metallic Bonding
Charge on cation Radius cation
Higher ↑ charge cation
Higher ↑ metallic bonding(melting point)
Bigger ↑ radius cation
Lower ↓ metallic bonding(melting point)
Higher ↑ number delocalized electrons
Why m/p Na (Gp 1) less than Mg (Gp 2) ?Why melting point
different?
ONE delocalized
electron per atomTWO delocalized
electron per atom
Radius cation Bigger ↑ Radius cation Smaller ↓
MELTING POINT MELTING POINT
Higher ↑ metallic bonding(melting point)
Charge cation smaller ↓ Charge cation Bigger ↑
• Temp when solid turn to liquid (temp remain constant)• Energy absorb to overcome forces attraction bet molecule
• Melting point across Period 2/3• Melting point down Gp 1
+1 +2
Heating mixture metals together
Alloy cool/solidifies, mechanical property diff from its individual constituentsMetals/non-metals often enhance its properties.
Induce strength/hardness by occupying empty spaces bet lattice structure
Metals • Same type of elements/atom arrangement• Malleable – shaped by hammering• Ductile –deform/ turn to wire
Aluminium- Soft/malleable
structure - crystalline lattice same type atoms
Click here for list of alloys
Metals Vs Alloy
Alloy• Mixture metals / non metal• Property alloy far superior than its element/metal• Stronger, harder and enhanced qualities than metals
structure - crystalline lattice different atomic sizes
Duralumin (Aluminium + Copper)Strong aircraft
Metals Alloy
Vs
Vs
Iron- Soft/malleable
Steel- Strong/Hard
What makes alloy strong?
Metal occupy spaces
in between
Heat mixture metals
Malleable (hammer) Ductile (Stretch)
Mixture of metals
in lattice
Strong + hard
✓
✓✗
✗
Click here uses alloy - nitinol robot
Metals
Structure - crystalline lattice same type atoms
Metals Vs Alloy
Property alloy far superiorthan its element/metal
Structure - crystalline lattice different atomic sizes
Vs
Malleable (hammer) Ductile (Stretch) Mixture of metals
in lattice
Alloy Component Property/Uses
Steel Iron + Carbon Structural material
Stainless steel Iron + Carbon +Nickel +Chromium Corrosion resistance
Brass Copper + Zinc Decorative
Bronze Copper + Tin Coins and medals
Duralumin Aluminium + Copper + Manganese Aircraft
Nichrome Nickel + Chromium Heating element
Pewter Tin + Copper + Antimony Decorative
Nitinol Nickel + Titanium Shape memory, actuator
Bold – Base main metal used
Same type atomarrangement
Ductile –Deform/turn to wire
Malleable –Shaped by hammer
Alloy
Mixture metals/non metal
Stronger, harder- enhance qualities than metals
+
✓
Metal + Metal = Alloy
Click here different alloys
Types of Alloy
Steel Stainless steel Brass Bronze
DuraluminNichrome
Pewter
Click here uses alloy - nitinol robot
✓
Crystalline Structure
Giant metallic Giant Ionic Giant Covalent Network
Simple Molecular
Non Polar Polar molecule H2 Bonding
Particles Atoms(Metals)Na, K, Li, Ca, Mg
Ion (+ve/-ve ions)Na+CI-, K+CI-
Atoms from Gp4 (Carbon/Silicon)
Molecules with Molecule with Molecule with H atom - Similar EN value - Different EN value - bonded to N, O, F- Bond polarity cancel – Dipole moment (electronegative atom) - Symmetrical - Asymmetrical
Bonding Lattice of positive ions with sea of electronsElectrostatic forces attraction bet +ion with electron
Lattice of positive and negative ionsElectrostatic forces attraction bet +ion with -ion
Giant covalent throughout 3D
structure.
Within molecule Within molecule Within molecule-strong covalent - strong covalent - strong covalentBetween molecule Between molecule Between molecule-weak intermolecular - weak intermolecular - weak intermolecular-VDF - VDF - VDF
- Dipole-dipole - Dipole -dipole- H2 bonding
PhysicalPropertyState
Solid(Non volatile)
Solid(Non volatile)
Solid(Non volatile)
Liq/Gas Liq/Gas Liq/Gas(Volatile) (Volatile) (Volatile)
MeltingPoint
HIGH HIGH VERY HIGH Very Low Very Low Very Low
Conduct Good Conductor-free moving electron
Good conductor-free moving ions in molten/aq state
Poor conductor- Diamond, SiO2Semiconductor- Graphite, C60Good conductor- Graphene
Poor conductor Poor conductor Poor conductor
Solubility Insoluble Soluble in polar solvent
Insoluble Soluble in polar Soluble in non polar Soluble in polar solventsolvent solvent
Sea electrons +ve / -ve ions
Strong CovalentMetallic Bonding Ionic Bonding
✓
CI CI
CI CI
CICI....
Between
moleculeWithin
molecule
....
Between
molecule
Within
moleculeH2 Bonding
Carbon atoms
Silicon atoms