The Solid State: Lattice Structure Flashcards
Giant covalent structures such as
graphite, diamond, sio2, graphene allotropes of carbon
structure and geometry of graphite
layered structure, geometrically planar. within planar layers, hexagonal C atoms.
C atoms in graphite
each C atom joined to adjacent 3 other by strong covalent bonds. sideways overlap of p orbitals, occupied by the 4th electron of each C atom in each planar layer form clouds of delocalised electrons above and below the plane of C rings and join up forming an extended delocalised rings of electrons.
colour and transparency of graphite
black-coloured, opaque
imf of graphite
layers of C atoms having weak van der waals’ forces
physical properties of graphite
high mp, high bp, soft, tender, slippery, good electrical conductor, insoluble in water
3 uses of graphite
pencils, lubricants, batteries
structure and geometry of diamond
C atoms arranged around each other regularly giving a crystalline structure and are geometrically tetrahedral
In diamond, each C atom bonded to
4 adjacent C atoms
colour and transparency of diamond
when pure, colourless and transparent
physical properties of diamond
high mp, high bp, the hardest natural substance on earth, good electrical insulator, insoluble in all solvents
3 uses of diamonds
gemstones, industrial abrasives, heat sinks
colour and transparency of sio2
they are colorless transparent crystals
physical properties of sio2
high mp, high bp, hard, good electrical insulator
3 uses of sio2
glass, ceramics, abrasives
shape of sio2
tetrahedral arrangement in which each Si atom bonded to 4 O atoms and each O atom bonded to 2 Si atoms
structure and geometry of graphene
it is a single isolated layer of graphite. hexagonally arranged sheet of C atoms
to what extent is the hardness of graphene
the hexagonally arranged sheet of C atoms is not completely rigid and can be distorted
reactivity of graphene
it is the most chemically reactive form of C
physical properties of graphene
high mp but burn at very low temperatures, good electrical and heat conductor (better than that of graphite)
3 uses of graphene
tiny transistors, touchscreens, solar cells
simple molecular structures such as
iodine and fullerene allotropes of C like C60 and nanotubes
distance between the nuclei of NEIGHBOURING iodine molecules … distance between the nuclei WITHIN the iodine molecule
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structure of iodine
regular packing of the molecules in a lattice structure
physical properties of iodine
low mp, low bp, is a semiconductor in the plane of its crystalline layers and an insulator in the perpendicular direction
disinfectants, printing inks, animal feed supplements, are 3 examples of uses of
iodine
in fullerene allotropes of C, each C atom is bonded to
3 adjacent other C atoms
other name of C60
buckminsterfullerene
explain the shape of C60
football shaped. C atoms arranged at the corners of 20 hexagons and 12 pentagons.
in C60, bond length between hexagons … between hexagons and pentagons
shorter than
Although both have each C atom bonded to 3 adjacent other C atoms, the extent of delocalised electrons in C60 is … than in graphite
lesser
physical properties of C60
low sublimation point, soft, poor electrical conductor, slightly soluble in solvents like carbon disulfide and methylbenzene
explain the reactivity of C60
more reactive than graphite or diamond. because it has a high electron density in certain parts.
antiviral treatment against HIV, cages for drug delivery in the body, are examples of uses of
C60
structure or geometry of nanotubes
hexagonally arranged C atoms like a single layer of graphite bent into the form of a cylinder
a simple molecular structure that is synthesized artificially
nanotubes
physical properties of nanotubes
very high melting points, very high tensile strength, high electrical conductivity, and better thermal conductivity than diamond
3 examples of uses of nanotubes
electrodes in paper-thin batteries, for added strength in clothing and sports equipment, used in the treatment of certain types of cancer
ionic substances are hard, but they are also brittle. explain the brittle property of ionic substances.
ionic crystals are split apart when hit in the same direction as layers of ions. this is because layers of ions are displaced by the force of the blow, then ions with the same charge come together, and repulsions between thousand of ions in the layers, all with the same charge, cause the crystals to split along these cleavage planes.
why is the metallic substance mercury a liquid at room temperature?
because some of the electrons in a mercury atom are bound MORE TIGHTLY than usual to the nucleus, WEAKENING the metallic bonds between atoms.
explain the heat conductivity property of metallic substances
they are good conductors of heat. their conduction of heat is partly due to the movement of delocalized electrons and partly due to the vibrations passed on from one metal ion to the next.
how do delocalised electrons move
they are free to move in a given direction, towards a positive charge or a more electronegative atom
explain the high tensile strength and hardness of metallic substances
in a metallic bond, the attractive forces between metal ions and delocalized electrons act in all directions.
explain the malleability and ductility of metallic substances
when layers slide, new metallic bonds reform easily between ions in new lattice positions and the delocalized electrons, which continue to hold ions in the lattice together.
explain the density of ice compared to water
in ice, there is a more open arrangement due to long hydrogen bonds, allowing h2o molecules to be slightly further apart than in the liquid, resulting in the density of ice being less than that of water.
structure of ice
three-dimensional hydrogen-bonded network of h2o molecules. a rigid lattice. each O atom surrounded by a tetrahedron of H atoms.
Allotrope
different crystalline or molecular forms of the same element. e.g. graphite and diamond are allotropes of carbon.
liquid state, vaporisation
the change in state when a liquid changes to vapour
liquid state, vapour pressure
the pressure exerted by a vapour in equilibrium with a liquid
explain the low sublimation point of C60
weak van der waals forces between each molecule and no continuous layered giant structure as in graphite
explain the softness of C60
does not require much energy to overcome the weak imf van der waals
explain high mps and bps in giant molecular lattices
a lot of energy needed to break strong covalent bonding between C atoms and separate the atoms throughout the structure
explain the hardness in diamond
difficult to break the three-dimensional network of strong covalent bonds between C atoms
explain the softness in graphite
it is easily scratched. the forces between layers of C atoms are weak. layers of graphite can slide over each other when a force is applied. the layers readily flake off.
explain the hardness of ionic lattices
takes a lot of energy to scratch the surface because of the strong attractive forces keeping ions together.
explain the high mp high bp of ionic lattices
the attraction between large numbers of oppositely charged ions in the lattice acts in all directions and bonds them strongly together.
explain the trend in mp bp with ions
the mp bp increase with the charge density on the ions. e.g. Mg2+ O2- magnesium oxide has higher melting point than Na+Cl- sodium chloride. this is because there is a greater electrostatic attraction between doubly charged ions than singly charged ions of similar size.
