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Giant Structures Bonding
Giant Structures Bonding
metallic bonding
Alloys are harder than pure metals
most metals we use are alloys
2 or more metals or metal and another element
different sized elements will make harder to slide so harder
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strong electrostatic forces between positive ions and shared negative electrons
hold atoms in regular structure
gives metal most of its properties
consist of giant structures
electrons in outer shell are delocalised
occur in metallic elements and alloys
strong forces so solid at room temp. and high bp & mp
delocalised electron so good conductor of heat & electricity
can slide over each other so malleable
Giant covalent structures
all bonded by strong covalent bonding
very high bp and mp
don't conduct electricity even molten except graphite
E.g
Diamond
Graphite
silicon dioxide (silica)
what sand is made of
each grain is GCS of silicon and oxygen
are macromolecules
Allotropes of Carbon
Graphite
contains sheets of hexagons
each C makes 3 covalent bonds
no covalent bond between layers so soft and slippery good for lubrication
high mp
only 3 of 4 C used in bonds other delocalised and free to conduct heat and electricity
Graphene
one layer of graphite
2 dimentional, one atom thick
incredily light and very strong so added as composite material to add strength without weight
conduct electricity, so good for electronics
Diamond
each C has 4 covalent bond in very rigid hard structure
very high mp
not conduct electricity as no free electrons
Fullerenes
can form closed tubes or hollow balls
arranged in hexagon but can have pentagon or heptagon
Sphere
Buckminsterfullerene
1st discovered
hollow sphere with 20 hexagon & 12 pentagons
can be used to cage other molecules
can be used to deliver drug to the body
have huge surface area, good for industrial catalyst
can make great lubricants
tube
can form nanotubes, tiny cabon cylinders
ratio of length to diameter is very high
can conduct electricity and thermal energy
high tensile strength, not break when stretched
can be used in electronics or to strengthen material without much weignt, eg tennis racket
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different structural form of same element in same state (solid)