bonding and physical properties Flashcards
solid -arangment of particles
regular .crystal shapes have straight edges .solids have definite shapes
solid-spacing
close -solids are not easily compressed
solid-movement
vibrating around a point -diffusion is very slow , solids expand upon heating
liquid-arrangement of particles
random -a liquid changed shape to fit the bottom of a container
liquid-spacing
close -liquids are not easily compressed
liquid-movement
rapid jolsting as diffusion is slow and liquids evaporate
gas-arrangement of particles
random as a gas will fill its container
gas-spacing
far apart as gases are easily compressed
gas-movement
rapid as diffusion is rapid and gases exert pressure
ionic compounds have strong electrostatic forces between….
oppisitley charged ions
do ionic compounds have high or low melting points ? explain
high as they have strong electrostatic forces that extend throughout the whole structure. these require a lot of energy to break in order for the ions to move apart from each other
do metallic crystals have a high or low melting point ? explain
high. attraction of positive to negative extended throughout the structure.strong metallic points
what are molecular crystals ?
molecules held in a array of regular inter molecular forces .covalent bonds act between the atoms in a molecule but not between the molecules
do molecular crystals have low or high melting points ?
low as inter molecular forces are much weaker than covalent ,ionic or metallic bonds
give the properties of molecular crystals ?
crystals are soft and break easy
low melting temperatures
do not carry electricity as their are no charged particles to carry it
what is a macromolecular crystal ?
A crystalline solid in which the atoms are all linked together by covalent bonds
do macromolecular strucutures have high or low melting temp?
high as they have strong bonds
what are diamond and graphite made up of ?
carbon , they are called allotropes of carbon
explain the structure of diamond ?
pure carbon with covalent bonding between every carbon atom .bonds spread throughout the structure which is why it is a giant structure .each carbon atom has for covalent bond to the other carbons .The four electron pairs repel each other ,, tetrehedron shape (with bond angles of 109.5)
explain the properties of diamond and give the reasons ?
a giant 3D shape with strong covalent bonds .
a very hard material
very high melting point
does not conduct electricity as their is no free charged particles to carry charge
what is the bonding in graphite ?
strong covalent and weaker van waals forces
explain the shape of molecules in graphite ?
each carbon atoms forms three other single covalent bonds to other carbon atoms .
form a flat trigonal arrangement. (sometimes called trigonal planar) ,120 .
describe the structure of bonding ?
two dimensional linked hexagons. spare electron in p orbitals merge above and below the plane of the carbon atoms ,these electrons can move anywhere in the layer, so they are delocalised which adds to the strength of the bonding
why does graphite conduct electricity ?
the delocalised electrons, they can travel freely in the material but only move along the hexagonal planes , not at right angles to them .
what bonds hold the layers of carbon together in graphite ?why does this matter ?
weak van der waals forces. it means the layers of carbon can easily slide over each other which makes graphite soft flaky
give the properties of graphite ?
soft material
very high melting point (due to strong network of covalent bonds which makes its a giant structure )
conducts electricity
