c2 - bonding Flashcards
what is ionic bonding?
when a metal reacts with a non-metal, this is ionic bonding
electrons are transferred
what happens when electrons are lost?
a positively charged ion is formed.
what happens when electrons are gained?
a negatively charged ion is formed
what holds ions together in a giant ionic lattice (+ and - arrangement)
electrostatic forces of attraction
what melting and boiling points do ionic compounds have?
Ionic compounds have very high melting and boiling points
Why?
The strong electrostatic forces require a lot of energy to break
can ionic compounds conduct electricity when their solid
Ionic compounds CANNOT conduct electricity when they are SOLID
Why?
This is because the ions cannot move (they are locked in place by the strong electrostatic forces of attraction)
what do we do to ionic compounds so they can conduct electricity?
They CAN CONDUCT ELECTRICITY when they are MELTED or DISSOLVED IN WATER
Why?
The ions are free to move and carry the charge
what does covalent bonding take place in
Covalent bonding takes place between non-metal
elements
A covalent bond is a shared pair of electrons
what are small covalent molecules at room temperature?
usually gases or liquids at room temperature
what melting and boiling point do small covalent bonds have?
low melting and boiling points
they do not conduct electricity
because they have weak forces between the molecules called intermolecular that are easy to overcome
what are giant covalent structures at room temperature
solid
what melting and boiling point do giant covalent bonds have
high melting and boiling points
why?
a lot of energy is needed to break the bonds
what is diamond made from?
Made from carbon
Each carbon atom forms 4 strong covalent bonds
can diamond conduct electricity?
it cannot conduct electricity
no free electrons to carry the charge
what is silica?
giant covalent structure
it has 4 strong covalent bonds
what melting and boiling point does silica have?
it has a high melting and boiling point because it needs a lot of energy to overcome the bonds
describe graphite
Giant covalent structure
Each carbon atom forms 3 covalent bonds
The carbon atoms form hexagonal rings
what are the properties of silica
Graphite is soft and slippery
Why?
It has layers that can slide over each other
Has a very high melting and boiling point
Why?
a lot of energy is needed to break the bonds
Graphite is an excellent conductor of both electricity and heat
Why?
delocalised electrons which can move between the layers
describe graphene
Graphene is a single layer of graphite
It is one atom thick
It is extremely strong
It is an excellent conductor of electricity BECAUSE IT HAS
DELOCALISED ELECTRONS
what are fullerenes?
Fullerenes are molecules of carbon atoms with HALLOW shapes
Usually, fullerenes have hexagonal rings of carbon atoms
1st fullerene to be discovered: Buckminsterfullerene (C^60)
what are the uses for fullerenes?
Uses:
- Pharmaceutical delivery
- Lubricants
- Catalysts
what are the uses of carbon nanotubes?
Fullerenes shaped into long cylinders
Uses:
- High tensile strength (can be stretched without breaking)
- Excellent conductors of heat and electricity
- Used to reinforce materials e.g. tennis rackets
What are polymers?
Polymers are made by joining together thousands of small,
identical molecules (monomers)
Monomers are often alkene molecules e.g. ethene
what are the properties of polymers?
Most polymers are solid at room temperare
The intermolecular forces of attraction between polymer
molecules are relatively strong so a lot of energy is needed to
break the bonds
describe metallic bonding
Metals consist of a giant structure of atoms arranged in regular
layers
The electrons in the outer energy level of each atom are
delocalised
what are the properties of metals
Metals can be bent and shaped
Why?
The layers of atoms are able to slide over each other
Metals have a high melting and boiling point
Why?
A lot of energy is needed to break the strong metallic bonds
Metals are excellent conductors of heat and electricity
Why?
The delocalised electrons can move and carry current
examples of pure metals
gold
copper
iron
They are not hard enough to be useful so we make alloys
what are alloys?
An alloy is a mixture of metals
The different sizes of atoms distorts the layers, making it more difficult for them to slide over each other
Alloys are harder than pure metals
Advantages and disadvantage of dot and cross diagram
advantage:
It is very clear where the electrons are coming from
disadvantage:
Do NOT tell us about the shape of the molecule
disadvantage of 2D stick diagram
disadvantage:
The covalent bond is shown as a stick - we can’t tell which electron in the bond came from which atom
No idea of outer electrons that are not in bonds
Do NOT give us accurate information on the shape of the molecule
advantage of 3D stick diagram
Shows the shape of the molecule
advantages and disadvantages of ball and stick diagram
advantage:
allows us to see the ions in 3 dimensions clearly
disadvantage:
in the diagram it shows the ions are widely spaced out when in reality they are packed together
- The model isn’t to scale: so the relative sizes of the ions are not shown
- In reality, there are no gaps between the ions
advantages and disadvantages of space-filling diagram
advantage:
gives us a better idea of how closely packed the ions are
disadvantages:
difficult to see the three-dimensional packing
Only shows the outer layer
