C3 Structure and Bonding Flashcards
What is an ion?
A charged particle when an atom loses or gains electrons
What happens when metals form ions?
They lose electrons to form positive ions
What happens when nonmetals form ions?
They gain electrons to form negative ions
What happens in ionic bonding?
When a metal and nonmetal react together the metal atom transfers electrons to the nonmetal forming a positive metal ion and negative nonmetal ion. These particles are strongly attracted by electrostatic forces
What do groups one and two lose in ionic bonding?
Electrons to form positive ions
What do groups six and seven gain in ionic bonding?
Electrons to form negative ions
What is the structure of ionic compounds?
A giant ionic lattice
Ions form closely packed regular lattice with very strong electrostatic forces of attraction between the oppositely charged ions in all directions.
What are the properties of ionic compounds?
High melting points and boiling points due to the strong bonds
When solid they cannot conduct electricity
When they melt they can carry electric charge
Some dissolve easily so can carry electric charge
Why can solid ionic structures not carry electric current?
The ions are held in place so cannot conduct electricity
What is covalent bonding?
When nonmetals bond together and share pairs of electrons
What are some limits of drawing covalent bonds?
In dot and cross diagram you cannot see the relative size of the atom or how it is arranged in space
In displayed formulas you cannot see the 3-D structure or where electrons come from
3D models can get confusing with large molecules
What are some properties of simple molecular substances that are covalently bonded?
They have strong covalent bonds but weak intermolecular forces
Melting and boiling points are very low as the intermolecular forces are weak
Larger molecules have stronger intermolecular forces so the melting and boiling points of these molecules increases
They do not conduct electricity as they are not charged
What is a polymer?
A long chain molecule that is formed by joining lots of small molecules (monomers) together
What state are polymers at room temperature and why?
Solid as polymers have larger intermolecular forces so more energy is needed to break them apart
Why are the boiling points of polymers lower than ionic or giant molecular compounds?
The intermolecular forces are weaker than ionic or covalent bonds
What is the structure of a giant covalent structure?
All atoms are bonded to each other by strong covalent bonds
What are the properties of giant covalent structures?
They have very high melting and boiling points
They don’t conduct electricity
What is an allotrope?
Different structural forms of the same element in the same physical state
What is the structure of diamond?
Each carbon atom is bonded to 4 other carbon atoms with covalent bonds
Why does diamond have a very high melting point?
Strong covalent bonds take a lot of energy to break
Why does diamonds not conduct electricity?
There are no free ions
What is the structure of graphite?
Each carbon atom is covalently bonded to 3 other carbon atoms.
There is one delocalised electron.
There are no covalent bonds between layers so they are free to move over each other
What are the properties of graphite?
Graphite is soft
It has a high melting point
It conducts electricity and Thermal energy
What is graphene?
A sheet of carbon atoms join together in hexagons
It is just one atom thick
What are the properties of graphene?
It is very strong and light
It conducts electricity through the whole structure
What are fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls
What is the structural arrangement of fullerenes?
Mainly arranged and hexagons but also pentagons and heptagons
What can fullerenes be used for?
Deliver drugs
Industrial catalysts
Lubricants
Electronics
Strength and composite materials
what are the three common states of matter?
solids
liquids
gases
what are the properties of solids?
hard to compress - particles are packed together in a regular pattern with no spaces
fixed shape and cannot flow - particles cannot move from place to place
what are the properties of liquids?
hard to compress - particles are close together with not many spaces
take the shape of a container + can flow - particles can move
what are the properties of gases?
easy to compress - widely spaced particles
spread out and fill container - particles move quickly and randomly
how can you change the state of a substance?
put in or take away energy
what happens when a substance changes from a solid to a liquid? (or a liquid to a gas)
energy is put into the solid (liquid)
this breaks the forces of attraction between the particles in the solid (liquid)
allowing the particles to move around
what causes a melting point/boiling point to be higher?
the stronger the forces of attraction between the particles, the greater amount of energy needed to break them
what are the limitations of the particle model?
it assumes all particles are solid spheres - particles actually have different shapes and are not solid
it is assumed that there are no forces in between the particles
what types of elements does ionic bonding ivolve?
metals and non-metals
why do small covalent molecules have low melting and boiling points?
they have weak intermolecular forces between the the molecules which do not require a lot of energy to break
why are giant covalent molecules solid at room temperature?
they have millions of strong covalent bonds so they have high melting and boiling points
what is diamond formed from?
carbon
Can diamonds conduct electricity? why? why not?
no
there are no free electrons to carry the charge
why does silicon dioxide have high melting and boiling points?
there are a huge number of strong covalent bonds which take a lot of energy to break
what are the properties of carbon nanotubes?
they have high tensile strength
good conductors
what is the difference between the bonding of a monomer and a polymer?
the monomer has a double carbon to carbon bond
the polymer has single carbon to carbon bonds
what are some key facts about repeating units of polymers?
only one carbon to carbon bond
the bonds on either side of the molecule have to extend out of the brackets
the n represents a large number
how are atoms in metals arranged?
giant structures in regular layers
what is metallic bonding?
the strong electrostatic attraction between the ‘sea’ of negative delocalised electrons and the positive metal ions
why do metals have high melting and boiling points?
it takes a lot of energy to break the metallic bonds
why are metals good conductors of heat and electricity?
the delocalised electrons can move and transfer energy
why are metals malleable?
the layers of atoms are able to slide over each other
what is an alloy?
a mixture of metals?
why are alloys harder than pure metals?
they different sizes of atoms distorts the layers, making it more difficult for them to slide over each other
what is the size of a micrometre in metres?
1 x 10^-6
what is the size of a nanometre in metres?
1 x 10^9
what is the size of coarse particles (PM10 or dust)?
1 x 10^-5 to 2.5 x 10^-6 metres
what is the diameter of fine particles?
100 to 2500 nanometres
or
1 x 10^-7 to 2.5 x 10^-6 metres
what is the diameter of nanoparticles?
1 - 100 nanometres
how many atoms do nanoparticles contain?
only a few hundred atoms
what happens to the surface area : volume ratio when the size of the particle falls?
as the size of the particle decreases by 10 times, the surface area : volume ratio increases by 10 times
why do you need a much smaller amount of nanoparticles compared to materials with normal particle sizes?
nanoparticles have a huge surface area to volume ratio so even a small amount of nanoparticles have a massive surface area
what are some uses of nanoparticles?
medicines
cosmetics
suncreams
deodorants
electronics
catalysts
what are some uses of nanoparticles?
medicines
cosmetics
suncreams
deodorants
electronics
catalysts
what are some risks of nanoparticles?
it is possible they can be absorbed into the body and enter the cells
what is an advantage of dot and cross diagrams?
it is clear where the electrons of each atom comes from as they are represented by dots and crosses
