2: Bonding, Structure, and the Properties of Matter Flashcards
what are the three types of bonding?
ionic, covalent, metallic
how does ionic bonding work?
metal atom reacts with a non-metal atom; electrons in the outer shell of the metal atom are transferred; metal atoms become positively charged ions; non-metal become negatively charged ions; the ions produced have noble gas configuration
what is the structure of an ionic compound?
lattice structure consisting of regular arrangement of alternating positive & negative ions; ions are closely packed together; strong electrostatic forces of attraction present between the oppositely charged ions; these act in all directions
what are negative ions called?
anions
what are positive ions called?
cations
what are the limitations of a dot-cross diagram?
does not show how the ions are arranged in space; don’t show the relative sizes of the atoms; do not show the intermolecular forces
what are the limitations of a ball and stick diagram / 3D models?
does not show bonds as forces, but as sticks - also creates illusion of space; not to scale; doesn’t show the forces of attraction between the ions; doesn’t show the movement of electrons to form the ions; 3D models - can’t see inside of the model
what are the limitations of a 2D model?
does not show where the ions are located on the other layers/the molecules shape; not to scale
how does covalent bonding work?
non-metal atoms share pairs of electrons - strong bond
what is the structure of a metal?
lattice structure; outer electrons become delocalised and are free to move throughout the structure; this means to atoms become positive ions
describe the properties of a solid
strong forces of attraction between particles; particles packed very closely together in a fixed, regular pattern; atoms vibrate about a fixed position; fixed volume and shape; high density; particles only have a small amount of energy
describe the properties of a liquid
weaker attractive forces than in solids; irregular, unfixed pattern - move and slide past each other - adopt the shape of the container they’re in; able to flow; fixed volume but not a fixed shape; moderate to high density; particles have more energy than those in a solid but less than gaseous particles
describe the properties in a gas
no intermolecular forces; random movement; no defined pattern; far apart and move quickly in all directions; collide with each other and with the sides of the container (pressure); no fixed volume; can be compressed; low density; highest amount of energy
if a substance’s temp is below it’s melting point, what state is it?
solid state
what is particle theory?
matter changes state depending on the energy and forces present between the particles in the substance; the amount of energy needed to change from a solid to a liquid and from a liquid to a gas depends on the relative strength of the forces acting between the particles - the stronger the forces between the particles the higher the melting point and boiling point
what are the limitations of particle theory?
considers all particles to be small, solid and inelastic spheres; doesn’t consider the difference caused by different particles such as atoms, ions or molecules or mixtures of all three; fails to consider the intermolecular forces that exist between different particles in different substances
what are the properties of ionic compounds?
high melting and boiling points due to the presence of strong electrostatic forces acting between the oppositely charged ions - require a lot of energy to overcome; when melted or dissolved in water, they conduct electricity - ions are free to move and so charge can flow
what are the properties of small molecules?
usually gases/liquids - have relatively low melting points and boiling points; volatile; weak intermolecular forces - don’t need a lot of energy to overcome; intermolecular forces increase with the size of the molecules - as there are more electrons, so larger molecules have higher melting and boiling points; poor conductors of electricity - no free ions or electrons to move and carry charge
what are the properties of polymers?
made up repeated monomers - linked by strong covalent bonds; relatively strong intermolecular forces acting in between polymer chains so usually solid at room temperature
what are the properties of giant covalent structures?
high melting and boiling points as they have many strong covalent bonds - large amounts of heat energy needed to overcome these forces and break down bonds- (most) cannot conduct electricity as they do not have free electrons nor charged particles - exceptions of graphite
what are the properties of metals?
very high melting and boiling points and are solids at room temperature, exception of mercury - bonds are very strong and are a result of the attraction between the positive metal ions and the negative delocalised electrons within the metal lattice structure; usually insoluble in water although some do react with it; good conductors of heat & electricity - delocalised electrons layers of atoms in metals can slide over each other - malleable and can be hammered and bent into shapes
what are alloys?
mixtures of metals with either other metals, or non-metals e.g. carbon, where the metals are mixed together physically but are not chemically combined
what are the properties of alloys?
have more strength, hardness or resistance to corrosion or extreme temperatures - than metals
why do alloys have different properties to metals?
they contain atoms of different sizes, which distorts the regular arrangements of atoms - makes it more difficult for the layers to slide over each other, so they are usually much harder than pure metals
why are metals good electrical conductors?
they have free electrons available to move and carry charge throughout the metal lattice structure.
why are metals good thermal conductors?
energy can be transferred by the delocalised electrons
describe the structure of diamond
each carbon atom bonds with four other carbons, forming a tetrahedron
describe the properties of diamond
does not conduct electricity; has a very high melting point; extremely hard and dense
why does diamond have its properties?
all the covalent bonds are identical, very strong and there are no weak intermolecular forces - making it very hard and meaning it has a high melting point, as lots of energy is needed to overcome the covalent bonds; there are no free electrons - it cannot conduct
what are the uses of diamond?
used in jewellery; for coating blades in cutting tools.
cutting edges of discs used to cut bricks and concrete are tipped with diamonds; heavy-duty drill bits and tooling equipment are also diamond tipped - due to it’s hardness
describe the structure of graphite
each carbon atom is bonded to three others forming layers of hexagonal shaped forms, leaving one free electron per carbon atom
why can graphite conduct electricity?
there is one free electron per carbon atom; these exist in between the layers and are free to move and carry charge
describe the properties of graphite
conducts electricity and heat; as a very high melting point; soft and slippery, less dense than diamond
why does graphite have these properties?
has free electrons to conduct; strong covalent bonds between carbon atoms require lots of energy to overcome; the layers are connected to each other by weak intermolecular forces only - the layers can slide over each other making graphite slippery and smooth
what are the uses of graphite?
used in pencils; as an industrial lubricant, in engines and in locks; used to make non-reactive electrodes for electrolysis
describe the structure of graphene
a single layer of graphite which is a sheet of carbon atoms covalently bonded forming hexagonal shapes
describe the properties of graphene
extremely strong; extremely light; can conduct electricity
why does graphene have these properties?
strong - it only has strong covalent bonds, no intermolecular forces; light - only one atom thick layer; conduction - has a free electron per carbon atom which can move and carry charge
what are the uses of graphene?
useful in fabricating composite materials; in electronics
describe the structure of fullerene
consist of molecules made only of carbon and which form hollow tubes or spheres
what are the uses of fullerene and why?
useful for targeted drug delivery systems - can be used to trap other molecules by forming around the target molecule and capturing it; useful for trapping catalyst molecules onto their surfaces making them easily accessible to reactants so catalysis can take place - have a huge surface area; some are excellent lubricants and are used in many industrial processes
describe the structure of Buckminsterfullerene (“Buckyballs”)
60 carbon atoms are joined together forming 20 hexagons and 12 pentagons which produce a hollow sphere
what is a nanotube?
Graphene that has been rolled into a cylinder to produce a type of fullerene
describe the properties of nanotubes
high tensile strength and are resistant to breaking or stretching; conducts electricity
give the uses of nanotubes
useful in composites and specialised materials, electronics and nanotechnology
how big are nanoparticles?
between 1 and 100 nanometres in size (diameter); usually contain only a few hundred atoms
how big are coarse particles?
2,500 to 10,000 nm (diameter) - often referred to as dust
how big are fine particles
100 - 2,500 nm (diameter)
why do nanoparticles make good catalysts?
they have a very high surface area to volume ratio;
the higher the ratio then the more surface area is available for reaction = the better the catalyst.
how can the s.a. to v. ratio be calculated?
ratio = surface area / volume
what are the uses of nanoparticles?
mainly used in catalysis - high surface area to volume ratios; titanium dioxide in nanoparticle form is used in sunscreens as it blocks UV light; fullerenes are used in medicine and drug design - more easily absorbed than other particles and can deliver drugs to target areas more effectively; also used in electronic circuitry and as coatings for artificial limbs and joints; nanoparticles of silver are sprayed onto the fibres of medical clothing and surgical masks - gives them the flexibility of a material & antibacterial properties of silver metal.
give an example of how the same chemical has different properties in bulk and nanoparticle form
titanium dioxide in nanoparticle form is used in sunscreens as it blocks UV light; also used in bulk form is used as a white pigment in paints
what are the risks of using nanoparticles?
still a lot of unknown factors and potential risks; lack of understanding on how they may affect health - although there haven’t been any serious short term side effects, there could be long term side effects which we haven’t detected yet as they haven’t been in use long enough; a small amount of toxicity in a particular nanoparticle would be multiplied due to the high surface area to volume ratio; this coupled with the fact that they are not easily disposed of by the body are a cause for caution in the medical application of nanoparticles.
