bonding and structure Flashcards
ionic bond
the attraction between oppositely charged ions
structure of an ionic compound
ionic lattice
properties of ionic compounds
- high melting and boiling points- strong ionic bonds that require a lot of energy to break
- cannot conduct electricity when solid, only when liquid- when solid, ions are not free to move and carry charge
when liquid, ions are free to move and carry charge
ionic bonding occurs between __________________________________
a metal and non-metal
how is an ionic bond formed
electrons are transfered from the metal to non-metal
definition of a covalent bond
a shared pair of electrons
definition of a molecule
2 or more atoms covalently bonded together
definition of diatomic
2 atoms covelantly bonded in a molecule
what types of elements are present in substances which contain covalent bonds
non-metals
2 types of covelant bonds
simple and giant
why do simple covelant substances have low melting and boiling points
have weak van der waals’ forces between the molecules which require little energy to break
why are simple covelant substances poor conductors of electricity
thye do not have delocalised electrons that can move and carry charge
properties of simple covelant substances
- low melting and boiling points
- they are soft and brittle
- poor conductors of electricity
- insoluble in water
examples of giant covelant structures
graphite
graphene (one layer of graphite)
diamond
why do giant covalent structures have hight melting and boiling points
have strong covelant bonds which require lots of energy to break
definition of an allotrope
different forms of the same element in the same state
in diamond each carbon atom is bonded to _____1._ other carbon atoms to form a _____2._____ structure
- 4
- tetrahedral
state the properties of diamond
- high melting and boiling points
- poor conductors of electricity
- hard
state the properties of graphite
- high melting and boiling points
- good conductors of electricity
- soft
state the properties of graphene
- high melting and boiling points
- good conductors of electricity
- hard
definition of a metallic bond
the attraction between delocalised electrons and a regular lattic of positive ions
properties of metals
- metals often have high melting and boiling points
- metals are good conductors of electricity
- metals are malleable and ductile
definition of malleable
can be hammared into shape
definition of ductile
can be drawn into a wire
why do metals usually have high melting and boiling points
metallic bond is strong and requires a lot of energy to break
why are metals good conductors of electricity
the electrons are delocalised and are free to move and carry the charge
why are metals malleable and ductile
layers (of ions) can slide over each other without disrupting the structure
definition of an alloy
a mixture of elements, at least one of which is a metal
why are alloys harder than pure metals
some of the ions (or atoms) in the alloy of a different size to those of the metal. this distorts the layers and makes it more difficult for the layers to slide over each other
equation to determine the % of gold in an alloy
number of carats/24 x 100
state a use of aluminium
overhead electrical wiring, alloys for aircraft
state a use of copper
electrical wiring, plumbing, brass, coinage
state a use of iron
bridges
state a use of magnesium
flares, high strength, low density alloys for aircraft
what is a nanoparticle
a structure that is 1-100nm in size and contains a few hundred atoms
why do nanoparticles have different properties and uses than the bulk material
high surface area to volume ratio
state a use of nanoparticles in sun cream
better skin coverage to the sun cream, more effective protection from u.v. rays, invisible on the skin, do not degrade on exposure to the sun
what are the potential risks of using nanoparticles
cell damage, harmful effects on the enviroment
