What is a molecule?
When atoms of the same element join together we get a molecule of that element.
What are the three types of strong chemical bonds?
Covalent, ionic and metallic
What are the particles like in ionic bonding?
The particles are oppositely charged ions
What are the particles like in covalent bonding?
The particles are atoms that share pairs of electrons
What are the particles like in metallic bonding?
The particles are atoms that share delocalised electrons
Where does ionic bonding occur?
It occurs in compounds that combine metals with non metals
Where does covalent bonding occur?
It occurs in most non-metallic elements and in compounds of non metals
Where does metallic bonding occur?
It occurs in metallic elements and alloys
In ionic bonding when a metal reacts with a non metal what happens?
Electrons in the outer shell of the metal atom are transferred
What happens when metal atoms lose electrons?
They become positively charged ions
What happens when a non metal gains electrons?
They become negatively charged ions
What ions that are produced have the same electronic structure as a noble gas?
Ions produced by metals in group 1 and 2 and by non metals in group 6 and 7
What is an ionic compound?
A giant structure of a ions
How are ionic compounds held together?
By strong electrostatic forces of attraction between oppositely charged ions
In which direction do the strong electrostatic forces act in an ionic bond?
They act in ALL directions
structure of sodium chloride
structure of sodium chloride
When atoms share pairs of electrons they form...
What may covalently bonded substances consist of?
Though some covalently bonded substances may have very large molecules like...
Some covalently bonded substances have giant covalent structures like...
Diamond and silicon dioxide
Metals consist of...
giant structures of atoms arranged in a regular pattern
The electrons in the outer shell of a metal atom are....
Delocalised and so are free to move around
Sharing of delocalised electrons gives rise to...
Strong metallic bonds
Where does freezing and melting take place at?
Where does boiling and condensing take place at?
What does the amount of energy need to change the state depend on?
The strength of the forces between the particles (In solids there are strong forces where in gases there are very weak forces)
The stronger the forces...
The higher the melting point and boiling point
What does the nature of the particles depend on?
The type of bonding and structure of the substance
What happens to the substance and the bonds between the particles when its being heated?
When a substance is heated, the temperature transfers energy to the particles until it reaches a point where it has enough energy to break the bonds meaning it changes state
What does the symbol (S) mean?
What does the symbol (l) mean?
What does the symbol (g) mean?
What does the symbol (aq) mean?
What are the structures like for ionic compounds?
Giant ionic lattices
What are the forces of attraction like in ionic compounds?
They have strong electrostatic forces of attraction in all directions between oppositely charged ions
Why do ionic compound have high melting and boiling points?
Because large amounts of energy are needed to break the strong bonds
When and Why do ionic compounds conduct electricity?
When they are melted or dissolved in water the ions are free to move around so charge can flow
Substances that consist of small molecules are usually...
liquids or gases that have relatively low melting and boiling points
Why do substances consisting of small molecules have low melting and boiling points despite having strong covalent bonds?
They have weak intermolecular forces
How do intermolecular forces get bigger?
When the molecules get bigger so larger molecules have higher melting and boiling points
simple molecular substances have strong covalent bonds True or false?
Do substances with small molecules conduct electricity?
No as they do not have an overall electric charge so there are no free ions
What needs to be overcome in order for the simple molecular substance to change state?
the intermolecular forces not the covalent bonds
How big are molecules in polymers?
Polymers have very large molecules
How are the atoms joined together in a polymer?
by very strong covalent bonds
Are the intermolecular forces between the molecules strong?
Yes the intermolecular forces are relatively strong
What state is a polymer in at room temperature?
Substances that consist of giant covalent structures are...
solids with very high melting points
How are atoms linked in giant covalent structures?
Strong covalant bonds that need to be overcome to melt or boil these substances
Name some examples of giant covalent structures
Diamond and graphite(forms of carbon) , sillicon dioxide (sillica)
Diagrams of giant covalent structures -
need to be able to recognise them
giant structures of atoms with strong metallic bonds which means most metals have high melting and boiling points
How are atoms arranged in pure metals?
They're arranaged in layers which allow them to be bent and shaped
Why are pure metals mixed with other metals?
To make alloys which are harder as pure metals are too soft for many uses
Why are alloys harder than pure metals?
Different elements have different size atoms so when when another element is mixed with a pure metal, the new atosm will distort the layers making it harder for them to slide over each other making the alloy harder
Why are metals good conductors of electricity?
They have delocolised electrons that carry electrical charge through the metal
Whya re metals good conductors of thermal energy?
Energy is transferred by the delocalised electrons
In a diamond each carbon atom...
forms four covalent bonds with other carbon atoms in a giant covalent structure
Is diamond very hard?
Does diamond conduct electricity?
no because there are no free ions or electrons
Does diamond have high melting point?
yes because there are strong covalent bonds
Does graphite conduct electricty and thermal energy?
One electron from each carbon atom is delocalised so yes
This makes it similar to metals as metals have delocalised electrons
In graphite each carbon atom forms...
Three covalent bonds woth other carbon atoms , forming layers of hexagonal rings which have no covalent bonds between the layers
Why is graphite ideal as a lubricating material>?
The layers are held together weakly meaning they're free to move over each other
This makes it soft amd slippery
Has graphite got a high melting point?
Yes because there are strong covalent bonds in the layers
Graphene is a sheet....
of carbon atoms joined togther in hexagons
Explain the properties of graphene in terms of its structure and bonding.
-The network of carbon atoms makes it very strong but as its only one atom thick its also very light
What is graphene useful for ?
electronics because it contains delocalised electrons which conduct electricity through the whole structure
- also composites because the arrangement of the carbon atoms makes it strong but also as it's one atom thick its also very light so it can improve strength without adding weight
describe a graphene diagram
What are fullerenes?
molecules of carbon atoms shaped like hollow balls
what is the structure of fullerenes based on?
hexagonal rings of carbon atoms but also may contain rings of 5 or 7 atoms
what was the first fullerene to be discovered?
Buckministerfullerene (spherical shape)
Can fullerenes form nanotubes?
what are nanotubes?
They are carbon cylindrical fullerenes with very high length top diameter ratios
Why are nanotubes useful?
Nanotubes can conduct electricity and heat
they are also very light
they have a very high tensile strength
they can be used in electronics because of this
they can add strength to an object without adding weight such as tennis racket frames
What are the uses of fullerenes?
-can deliver drugs as tehy can 'cage' other molecules
-can be used as lubricants
-carbon nanotubes (nanotechnology)
the structure of fullerenes