2-bonding structure and properties of matter Flashcards
how are ions formed when electrons are transferred
when atoms lose or gain electrons to form ions, theyre trying to get a full outer shell like a noble gas (stable electronic structure) as atoms with full outer shells are stable
when metals form ions they lose electrons from their outer shell to form positive ions
when non metals form ions they gain electrons into their outer shell to form negative ions
the number of electrons lost or gained is the same as the charge of the ions
(if 2 electrons are lost = 2+)
(if 2 electrons gained = 2-)
what is an ion
a charged particle
they can be single atoms like Cl-
or a group of atoms NO3-
why are group 1 and 2
and group 6 and 7
most likely to form ions
g1 and g2 are metals and they lose electrons to form positive iosn (cations)
g6 and g7 are non metals that gain electrons to form negative iosn (anions)
group 1 form 1+ ions
group 2 forms 2+ ions
group 6 forms 2- ions
group 7 forms 1- ions
why are group 1 and 2
and group 6 and 7
most likely to form ions
g1 and g2 are metals and they lose electrons to form positive iosn (cations)
g6 and g7 are non metals that gain electrons to form negative iosn (anions)
group 1 form 1+ ions
group 2 forms 2+ ions
group 6 forms 2- ions
group 7 forms 1- ions
show the ionisation equations for
sodium
magnesium
chlorine
oxygen
1-sodium: loses 1 electron to form sodium ion with same electronic structure as neon
Na => Na+ +e-
2=magnesium: loses 2 electrons to form a magnesiumion with same electronic structure as neon
Mg => Mg2+ + 2e-
3= chlorine: gains 1 electron to form a chloride ion with same electronic structure as argon
Cl + e- => Cl-
4= oxygen: gains 2 electrons to form an oxide ion with same electronic structure as neon
O + 2e- => O2-
what is ionic bonding
when a metal and a non metal react together
the metal atom loses electrons to form a positively charged ion and the nonmetal gains these electrons to form a negatively charged ion
these oppositely charged ions are strongly attracted to one another by electrostatic forces
this attraction is called an ionic bond
what do dot and cross diagrams show
it shows the arrangement of electrons in an atom or ion
each electron is represented by a dot or cross
so these diagrams show which atom the electrons in an ion originally came from
they show how the ionic compound is formed but dont show the structure of the compound, thesize of the ions or how theyre arranged
what kind of structure do ionic compounds form
giant ionic lattice
ions form a closely packed regular lattice arrangment, theres strong electrostatic forces between oppositely charged ions in all directions in the lattice
e.g. a single crystal of sodium chloride(table salt ) is one giant ionic lattice. the Na+ & Cl- ions are held together in a regular lattice
how can giant ionic lattices be shown through diagrams
describe the 2 ways
1)model = shows relative size of ions,shows regular pattrn of ionic crystal but only shows outer layer of compound
2) ball and stick model shows regular pattern of an ionic crystal, shows how all ions are arranged, it suggests that the crystals extends beyond whats shown in the diagram
but model isnt to scale so relative sizes of ions may not be shown and in reality there are not gaps between the ions e.g. in Na+ and Cl- ions are alternate
what are all the similar properties of ionic compounds
high melting and boiling point due to many strong bonds between the ions, takes a lot if energy to overcome this attraction
when solid, the ions are held in place so compounds cant conduct electricity, when ionic compounds melt,ions are free to move so theyll carry electric current
some ionic compounds also dissolve in water, ions separate are all free to move in solution so theyll carry electric current
How to find empirical formula of an ionic compound
from the diagram of a compound
if its dot&cross= count up how many atoms there are of each element to get empirical formula
if you have 3d diagram of ionic lattice, use it to work out what ions are in the ionic compound
then balance charges of the ions so that overall chargge on compound is 0
e.g. a compound with potassium and oxide ions
potassium is g1 so 1+ ions
oxygen is g6 so 2- ions
potassium ion only has a 1+ charge sp you need 2 of them to balance out 2- charge of oxideion so K2O
explain how covalent bonding works
when nonmetals atoms bond together they share pairs of electrons to make covalent bonds
positively charged nuclei of bonded atoms are attracted to the shared pair of electrons by electrostatc forces making covalent bonds very strong
atoms only share electrons in their outer shells(energy level)
each single covalent bond provides one extra shared electron for each atom
each atom involved generally makes enough covalent bonds to fill up its outer shell. full outer shell gives them the electronic structure of a noble gas=stable
covalent bonding happens in compounds of non metals (H2O) and in non metal elements (Cl2)
how can you show covalent bonding with dot and cross diagram
dot and cross diagram =overlap between outer orbitals of 2 atoms are shared between those atoms
they are useful for showing which atoms the electrons in a covalent bond come from
but they dont show the relative sizes of the atoms or how the atoms are arranged in space
vhow can you show covalent bonding with the displayed formula
shows covalent bonds as single lines between atoms
its good for showing how atoms are connected in large molecules
but they dont show 3D structure of molecule or which atoms the electrons in the covalent bond have come from
how can you show covalent bonding with 3D model
it shows atoms, covalent bonds, arrangement in space next to each other
but 3D models can quickly get confusing for large molecules where there are lots of atoms to include
they dont show where the electrons in the bonds have come from either
how can you find the molecular formula of a simple molecular compound from any of the 3 diagrams
count up how many atoms of each element there are
H H
| |
e.g. H -C-C- H
| |
H H
so it is C2H6
what are simple molecular substances and give examples
they are made up of molecules containing a few atoms joined together by covalent bonds
hydrogen - H2
has 1 electron to complete 1st shell so they form single covalent bonds with hydrogen atoms or with other elements
oxygen- O2
each oxygen atom needs 2 more electrons to complete its outer shell so in oxygen gas, 2 oxygen atoms share 2 pairs of electrons with each other making a double covalent bond
methane CH4
carbon has 4 outer electrons which is half a full shell
forms 4 covalent bonds with hydrogen atoms to fill outer shell
chlorine Cl2
each atom needs 1 more electron to complete outer shell so 2 chlroine atoms can hare 1 pair of electrons and form a single covalentbond
nitrogen N2
they need 3 more electron so 2 nitrogen atoms share 3 pairs of electrons to fill their outer shells to make triple bond
water H2O
water molecules, oxygen shares a pair of electrons with 2 H atoms to form 2 single covalent bonds
hydrogen chloride HCl
both atoms need one more electron to complete their outer shells
what are properties of simple molecular substances substances containing covalent bonds
1- atoms held together by strong covalent bonds but forces of attraction between molecules are very weak
2-to melt or boil a simple molecular compound you only need to break feeble intermolecular forces and not covalent bonds so melting and boiling point is very low because molecules are easily parted from each other
3-most are gases or liquids at room temp
4- as molecules get bigger, strength of intermolecular forces increase so more energy needed to break them and melting and boiling point increases
5-molecular compounds dont conduct electricity bc they are not charged so no free electrons or ions
what are polymers
lots of small units linked together to form a long molecule that has repeating sections
all the atoms in a polymer are joined by strong covalent bonds
how do you show polymers through diagram
draw the shortest repeating section called repeating unit
the part in the bracket is the repeating unit
‘n’ is the large number tell you the unit has repeated lots of times
bonds through the brackets join up to the next repeating unit
explain how intermolecular forces work in polymer molecules
they are larger than the ones in simple covalent molecules so more energy is needed to break them so most polymers are solid at room temperature
intermolecular forces are still weaker than ionic or covalent bonds so they generally have lower boiling points than ionic and giant molecular compounds
why are giant covalent structures macromolecules
all atoms are bonded to each other by strong covalent bonds
high melting and boiling point as lots of energy is needed to break the covalent bonds between atoms
dont contain charged particles so dont conduct electricity not even when molten (except for things like graphite)
main examples are diamond and graphite both made from carbon atoms only and silicon dioxide
why are giant covalent structures macromolecules
all atoms are bonded to each other by strong covalent bonds
high melting and boiling point as lots of energy is needed to break the covalent bonds between atoms
dont contain charged particles so dont conduct electricity not even when molten (except for things like graphite)
main examples are diamond and graphite both made from carbon atoms only and silicon dioxide
explain how diamonds are structured
each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure
explain how graphite is structured
each carbon atom forms 3 covalent bonds to create layers of hexagons
each carbon atom also has 1 delocalised free electron
explain how silicon dioxide is structured
sometimes called silica
what sand is made from
each grain of sand is 1 giant structure of silicon and oxygen
explain properties of diamond
giant covalent structure made up of carbon atoms that each form 4 covalent bonds making diamond rlly hard
strong covalent bonds take a lot of energy to break so it has a high melting point
doesnt conduct electricity bc it has no free electrons or ions
explain properties of graphite
each carbon atom forms 3 covalent bonds creating sheets of carbon atoms arranged in hexagons
arent any covalent bonds between the layer, only held together weakly so theyre free to move over each other
it is soft and slippery so ideal for lubricating material
high melting point bc covalent bonds in layers need loads of energy to break
only 3 out of each carbon’’s 4 outer ekectrons are used in bonds so each carbon atom has 1 electron that is delocalised, free to move
so it can conduct electricity and thermal energy
explain graphene
graphene is one layer of graphite
its a sheet of carbon atoms joined togehter in hexagons
sheet is 1 atom thick making it a 2d compound
network of covalent bonds makes it very strong
it is incredibly light so can be added to composite materials to improve their strength without adding much weight
like graphite, it contains delocalised electrons so can conduct electricity through whole structure, so it can be used in electronics
what are fullerenes
are molecules of carbon
shaped like closed tubes or hollow balls
what is buckministerfullerene
first fullerene to be discovered
molecular formula is C60 and forms a hollow sphere
what are fullerenes made up of
what can they be used for
made up of carbon atoms arranged in hexagons
can also contain pentagons(rings of 5 carbon atoms)
or heptagons (rings of 7 carbon atoms)
they have a huge surface area so they make good industrial catalysts (individual catalyst molecules could be attached to the fullerenes, fullerenes also make great lubricants)
they can be used to cage other molecules
fullerene structure forms around another atom or molecule which is then trapped inside
(could be used to deliver a drug into the body)
what are nanotubes and how do fullerens form them
fullerenes can form nanotubes which are tiny carbon cylinders
ratio betwee length and diameter of nanotubes are very high
nanotubes can conduct both electric and thermal energy(heat)
also has high tensile strength (dont break when stretched)
technology using small particles such as nanotubes is called nanotechnology
nanotubes can be used in electronics or to strengthen materials without adding much weight e.g. tennis racket frame
explain how metallic bonding works
metals also consist of a giant structure
electrons in the outer shell of the metal atoms are delocalised (free to move) there are strong forces of electrostatic attraction between the positive metal ions and the shared negative electrons
these forces of attraction hold the atoms together in a regular structure =metallic bonding
it is very strong
substances held together by metallic bonding = metallic elements and alloys
its delocalised electrons in the metallic bonds produce all properties of metals
why are metals solid at room temperature
electrostatic forces between metal atoms and delocalised sea of electrons are strong so needs lots of energy to be broken
the most compounds with metallic bonds have very high melting and boiling points so theyre generally solid at room temp
why are metals good conductors of electricity and heat
delocalised electrons carry electrical current and thermal heat energy through the whole structure so metals are good conductors of heat and electricity
why are metals good conductors of electricity and heat
delocalised electrons carry electrical current and thermal heat energy through the whole structure so metals are good conductors of heat and electricity
why are most metals malleable
layers of atoms in a metal can slide over each other making metals malleable
so they can be bent or hammered or rolled into flat sheets
why are alloys harder than pure metals
pure metals often arent right for certain jobs, too soft when theyre pure so theyre mixed with other metals to make them harder
most of the metals used everyday are alloys = a mixture of 2 or more metals or a metal and another element, alloys are harder so theyre more useful than pure metals
different elements have different sized atoms, so when another element is mixed with a pure metal, the new metal atoms will distort the layers of the metal atoms making it more difficult for them to slide over each other, this makes alloys harder than oure metals
what does the state of something depend on
how strong the forces attraction are between the particles of the material which depends on
material(structure of substance, type of bonds holding it together)
temperature
pressure
explain arrangement of solids
strong forces of attraction between particles which holds them close together in fixed positions to form regular lattice arrangement
particles dont more from their positions so all solids keep definite shape and volume
particles viibrate in fixed position
hotter the solid becomes the more they vibrate (causing solids to expand slightly when heated)
explain arrangement of solids
strong forces of attraction between particles which holds them close together in fixed positions to form regular lattice arrangement
particles dont more from their positions so all solids keep definite shape and volume
particles viibrate in fixed position
hotter the solid becomes the more they vibrate (causing solids to expand slightly when heated)
explain arrangement of liquids
weak force of attraction between particles
randomly arranged and free to move past each other but tend to stick closely togehter
has definite volume
doesnt have definite shape but will flow to fill bottom of a container
particles constantly moving with random motion
hotter the liquid, faster it moves causes liquids to expand slightly when heated
explain arrangement of gas
forces of attraction between particles is veryweak
theyre free to move and are far apart
particles in gases travel in straight lines
they dont keep definite shape/volume and will always fill any container
particles constantly move with random motion
the hotter the gas gets, the faster they move
gases expand when heated or pressure increases
advantages and disadvantages of particle theory
great model for explaining the 3 states of matteer
but
particles arent solid or inelastic and they arent spheres
theyre atoms,ions or molecules
model doesnt show forces between the particles so theres no way in showing how strong they are
what are the state symbols
for solids
liquid
gas
aqueous
solid is s
liquid is l
gas is g
aqueous is aq
explain the change in particle arrangement when solid melts to become liquid
when solid is heated particles gain more energy
particles vibrate more which weakens forces holding solid together
at a certain temperature (melting point) particles have enough energy to break free from positions
this is melting aand solid becomes liquid
explain boiling/evaporating from liquid to gas
when a liquid is heated again,the particles get even more energy
energy makes particles move faster which weakens and breaks bonds holding the liquid together
at a certain temp(boiling point) particles have enough energy to break bonds =this is boiling/evaporating
liquid becomes a gas
explain condensation from a gas to a liquid
as gas cools
particles no longer have enough energy to overcome the forces of attraction between them
bonds then form between the particles
at the boiling point so many bonds have formed between gas particles that the gas has become a liquid= condensing
explain freezing from a liquid to a gas
when a lquid cools, the particles have less energy so moves around less
theres not enough energy to overcome the attraction between the particles so more bonds form between them
at the melting point
so many bonds have formed between the particles that theyre held in place so the liquid becomes a solid
this is freezing
what does the amount of energy needed for a substance to change state depend on
how strong the forces between the particles are
the stronger the forces= the more energy is needed to break them so the higher the melting and boiling point is of the substance
how can predict the state of a substance at a certain substance
if temp is below the melting point of a substance it will be a solid
if its above the boiling point it will be a gas
if its between 2 points,its a liquid
what categories are particles put into depending on size of their diameter
coarse particles
fine particles
nanoparticles
explain coarse particles
PM10
diameter is between
2500 nm (2.5 x 10^-6) and 10 000 nm (1x10^-5m)
it is also called dust
explain fine particles
PM2.5
diameter between
100nm (1x10^-7) and 2500nm (2.5x10^-6m)
explain nano particles
diameter is between 1nm (1 x 10^-9 m) and 100nm(1x10^-7m)
these are particles that contain only a few hundred atoms
there is a whole area of science investigating uses and propeties of nanoparticles called nanoscience
nanoparticles have a large surface area to volume ratio, surface area is very large compared to volume
explain how to calculate surface area to volume ratio
surface area / volume
total surface area= x surface area by number of faces
as particles decrease in size,the size of their surface area increases in relation to their volume causing the surface area to volume ratio to increase
as you decrease the side of any cube by a factor of 10, the surface area to volume ratio will always increase by a factor of 10
what does it mean if nanoparticles have a high surface area to volume ratio
surface area is large compared to the volume
this can cause the properties of a material to be different depending on whether its a nanoparticle or whether its in bulk
e.g youll often need less of a material that is made up of nanoparticles to work as an effective catalyst compared to a material made up of normal sized particles containing billions of atoms rathher than a few hundred
what can nanoparticles be used for
1-huge surface area to volume ratio so they can help make new catalysts
2-nanomedicine, tiny particles (e.g. fullerenes) are absorbed more easily by the body than most particles
this means they could deliver drugs right into the cells where theyre needed
3- nanoparticles can conduct electricity so can be used in tiny electric circuits for computer chips
4- silver nanoparticles have antibacterial properties #, can be added to polymer fibres used to make surgical masks and wound dressings, can also be used in deodorants
5- used in cosmetics e.g. used to improve moisturisers without making them really oily
issues involved with nanoparticles being in products
the way nanoparticles affect the body is not fully understood so its important that new products are tested thoroughly to minimise the risks
-products with nanoparticles have been available before effects on human health have been investigated properly so we dont know what long term impacts on health will be
-as long as long term impacts are not known, many believe products containing nanoscale particles should be clearly labelled so consumers can choose whether or not to use them
why are nanoparticles used in sun creams
what are issues with this
they have been shown to be better than the materials in traditional in sun creams at protecting skin from harmful UV rays
-better skin coverage than traditional suncreams
but its not clear yet whether nanoparticles can get into your body, if they do they might damage cells
they might damage the environment
