chem 2 Flashcards
which types of elements form covenant bonds
non metals
which types of elements form ionic bonds
non metal and non metal
what is a covelant bond
chemical bond where two atoms share one or more pairs of electrons to achieve stability
why do some structures form giant covalent structures
need for maximum bonding
achieving stability
atoms with high electronegativity and small size
why do ionic substances have high melting points ?
strong electrostatic (ionic) bonds and lattice structure that requires a lot of energy to break
what element is contained in both diamond and graphite
carbon
why does graphite conduct electricity
due to delocalised electrons that can move freely
due to weak van der Waals forces allowing the delocalised electrons to move freely due
how many bonds does each carbon atom in a diamond form
4
why is graphite slippery and soft
because of its unique layered structure and the weak forces between those layers.
what holds metals together
electrostatic attraction, which is the reason metals are so strongly joined
what is a polymer
a very long molecule made of many units
what is an alloy
an alloy is a mixture of two or more elements, where at least one is a **metal
why are alloys harder than pure metals
because they are irregularly arranged which means more energy is needed to separate the bonds as there are no layers
what is electrostatic attraction
the force of attraction between opposite electric charges (positive and negative).
what is a nanoparticle
a particle with dimensions between 1 and 100 nanometers (nm)
what atoms are in simple covalent bonds
non metal
what types of atoms are in giant covalent bonds
non metals
what types of atoms are in polymer bonds
non metals
what are the melting points of simple covalent bonds and why
low MP n BP
weak bonds between them
what are the melting points of giant covelant bonds and why
high MP n BP
strong covalent forces between them
what are the melting points of polymer bonds and why
low MP n BP
weak intermolecular covalent bonds
what are the melting points of metallic bonds and why
moderate to high MP n BP
due to sea of delocalised electrons
positively charged metal ions in lattice structure
more valence electrons
what is the state of ionic bonds at room temp
solid
what is the state of simple covalent bonds at room temp
gas, occasionally liquid
what is the state of giant covalent bonds at room temp
solid
what is the state of polymers at room temp
solid
what is the state of metallic bonds at room temp
solid
what are the two types of polymers
thermosetting and thermosoftening
what are the two variables that change a polymer
the monomers it’s made from
the conditions the polymer is made in
how big is a fine particle
100-2500nm
how big is a coarse particle
2500nm-10,000nm
what is the use of a nanoparticle
medicine, electronics, cosmetics and sun cream
what are risks of nanoparticles
small size may make it possible to breathe in or for them to pass into cells
what are coarse particles sometimes referred to as
dust, grit
what type of structure is found in diamonds
giant lattice from compression; also has high MP n BP
what is an ionic bond
a bond formed with electrostatic attraction between oppositely charged atoms where electrons are transferred
what are delocalised electrons
electrons that aren’t in their arranged place
why are metals good conductors of thermal energy
due to having delocalised electrons
metals are sonorous, what is it?
the ability of a material (typically metals) to produce a deep, resonant, ringing sound when struck.
metals are ductile, what’s that?
to be able to be stretched thin without breaking
what are properties of metals?
mostly soft
good conductor of heat and electricity
high density
typically malleable
why can pure metals be shaped easily?
their regular arrangement makes the possibility of layers being blanket slide on top of each other
why are pure metals mixed with other metals or elements to make alloys
due to their versatility and harder nature
what causes metallic bonding?
when an atom/molecule loses or gains electron(s)
list some uses of alloys
pots, pans, automotive, aerospace, construction
what’s the composition of bronze
mosyly copper and some tin
what’s the composition of brass
mostly copper, some zinc
what’s the composition of gold in jewellery
mostly pure gold with alloys
what is steel
alloy of carbon and iron
properties of high carbon steel
brittle, strong, harder
properties of low carbon steel
malleable, lower strength
composition of stainless steel
iron, chromium, nickel and other
density of aluminium alloys
mostly lightweight
why can ionic substances conduct electricity when melted or in water
because the ions are free to move, allowing them to carry an electric current
what is the structure of an ionic compound
giant ion lattice
examples of covalent bonded substances
H2O, CO2, methane
state the name of a covalent bonded substance that is made of very large molecules
polyethene
what properties do substances which consist of small molecules usually have
weak intermolecular forces
softness
solubility
How do the intermolecular forces change as the size of the molecule increases?
Forces get stronger
how do the melting and boiling points of substances change as the size of the molecule increases?
Melting and boiling points increase
describe the physical properties of giant covalent structures
High melting and boiling points, hard, and poor electric conductivity
what must happen in giant covalent substances in order for them to melt or boil?
must reach high temp
what type of substance are diamond graphite and silicon dioxide examples of
minerals
describe the type of particles in covalent substances
molecules
why can graphene conduct electricity
it has a hexagonal lattice which allows for the presence of delocalised electrons
what is grapheneused for?
electronics
what are fullerenes?
a class of carbon allotropes that consist of spherical, ellipsoidal, or cylindrical structures made entirely of carbon
what is the fullrene with the formula C60
buckminsterfullrene
what shape does a buckminsterfullrene have
football, 20 hexagonal and 12 pentagonal faces
describe the forces that are present between the molecules of buckminsterfullerene
van der Walls, intermollecular
explain the melting points of Buckminsterfullrene
low
due to weak van der Walls, intermolecular forces
States one use of fullrenes
drug delivery systems
describe the structure of carbon nano tubes
cylindrical and made of rolled up graphene electrons
describe the tensile strength of nano tubes
Very high strength
and carbon nanotubes conduct electricity
yes, depending on their structure, e.g. metallic or semiconducting
describe the structure of graphite
layered two dimensional hexagon lattice
describe the strength of the forces in between the layers of graphite
weak van der Walls forces
describe the structure of graphene
Single layer of carbon atoms
how do strong bonds affect the melting points of graphene
it would raise the melting points and boiling points
why can graphite be used as a lubricant
it’s has layers which can easily slide on top of each other alongside intermolecular forces
describe the strengths and limitations of a Dot and cross model to show ionic bonding
strength is that it’s clearly shows transfer of electrons limitation is that it’s oversimplifies bonding i’m not showing the true size of the ions
describe the strengths and limitations of a ball and stick model to show ionic structure
Clear 3-D representation of ionic structure
however may not represents real relative size
describe the strengths and weaknesses of a 3-D diagram of an ionic lattice to show ionic structures
realistic view of arrangements
complex and hard to interpret for people that are unexperienced
describe the strengths and weaknesses of a 2-D diagram of an ionic lattice to show ionic structures
simplify the representation for easy interpretation
does not show 3-D nature of structure
What does nano science refer to?
The study of structures and materials between 1 to 100 nm
what’s a nano tubes used for?
electronics and medicine
why are smaller quantities of nano particles as effective as a larger quantities of materials with larger particles sizes?
higher reactivity and targeted delivery
Why do nano particles have different properties from the same materials in bulk?
Surface area to volume ratio increases dramatically
what is the monomer that makes up both low density polyethene and high density polyethene
ethylene
why are polymers generally solids at room temperature?
van der walls forces
