Structure and bonding Flashcards
Electrostatic forces
Force between the oppositely charged particles
which causes covalent and ionic bonds to be strong.
Intermolecular forces
Force between each simple covalent molecule. When broken, doesn’t break the bonds but causes a change in state.
Ionic compounds - what melting + boiling points and why?
High
Because the oppositely charged ions are held together by strong electrostatic forces
It takes a lot of energy to break these forces between ions
So it has a high melting point so solid at room temperature
Ionic compounds - do they conduct electricity and why?
Only when dissolved in water or molten
Because it has a giant ionic lattice structure
When it is solid the ions are in a fixed place and cannot move
Therefore they cannot carry a charge
When melted or dissolved the ions are free to move
So they can therefore carry a charge
Why are covalent bonds strong?
Both the nucleus in each atoms (positive) is strongly attracted to the shared electrons in the outer shell (negative).
So electrostatic attraction
Simple molecules - what melting and boiling points and why?
Low
Because it has weak intermolecular forces
Little energy is needed to overcome these weak forces
So it has a low boiling point and is a gas at room temperature
Simple molecules - do they conduct electricity and why?
No
It has no delocalised electrons or ions
So has no particles to carry a charge
What is a giant covalent structure?
Millions of atoms joined together by covalent bonds that are arranged in a lattice shape.
Do giant covalent structures have high or low boiling/melting points? Why?
Very high
Because it has a giant covalent structure
With millions of covalent bonds between the many atoms
So a lot of energy is needed to overcome their strong covalent bonds
So has high melting/boiling point and a solid at room temperature
Metallic bonding
Bonding in metal elements due to sea of delocalised electrons moving
And the electrostatic attraction between the electrons and positive metal ions
Do metal bonds conduct electricity?
Yes
They have a giant metallic lattice structure
So has delocalised electrons
That can move through a structure carrying a charge
Do metal bonds have high or low melting/boiling points?
High
Have a giant metallic lattice structure
The positive metal ions are held together by delocalised electrons
This strong electrostatic attraction takes a lot of energy to overcome and pull the ions apart
So have a high melting point
Are metal bonds soft?
Yes, because the metal atoms are arranged in layers so when a force is applied they slide over each other
Alloy
Mixture of 2 or more elements, where at least one is a metal. Usually 2 metals in order to increase hardness of pure metals.
Why are alloys harder than pure metals?
Many different sized atoms due to multiple elements so greater force needed to make layers slide over each other
The layers are DISTORTED
What bonding forms giant structures?
All 3: giant ionic lattices, giant covalent structures and giant metallic structures
Polymer
A large molecule made up of many small units (monomers)
Are the bonds between atoms in a polymer weak or strong?
Strong because it’s joined by covalent bonds which are strong
What holds ionic compounds together?
Electrostatic forces
How can metals and graphite conduct electricity?
Because they both have delocalised electrons that can conduct heat
Fullerene
Molecules of carbon atoms with hollow shapes
Normally made out of hexagonal rings
Are ionic compounds molecules?
No because a molecules is 2 or more atoms held together by COVALENT bonds
What forms graphite?
Carbon atom covalently bonded to 3 other carbon atoms
In hexagonal rings
Then large rings are in layers with no bonds between
Properties of graphite
High melting and boiling point
Soft and slippery
Good conductor of heat and elec
Why does graphite have high melting and boiling points?
It takes a lot of energy to break covalent bonds
Why is graphite slippery?
The hexagonal rings the carbon atoms are in are in layers
No covalent bonds between the layers = they can slide
Therefore it’s slippery
Why is graphite good conductor of heat and elec?
Because the C atoms form 3 other singular covalent bonds
So has a spare electron that isn’t shared as carbon has 4 electrons in outer shell therefore there is one free electron
Which is released in the outer shell
To be delocalised and move between layers and conduct electricity
What makes up diamond?
4 carbon atoms covalently bonded with 4 other carbons
Millions of these
Properties of diamond
High melting and boiling point
Cannot conduct electricity
Why does diamond have high melting and boiling points?
Because it contains millions of carbon atoms covalently bonded
To melt requires breaking these millions of bonds
Which require a lot of energy
Why does diamond not conduct electricity?
It has no free electrons to carry electrical charge
What makes up silicon dioxide?
Silicon atom bonded covalently with 4 oxygen atoms
Millions of these
Properties of silicon dioxide
Very high melting and boiling point
Why does silicon dioxide have high melting and boiling point?
Because it contains many covalent bonds that require a lot of energy to break
What makes up graphene?
Single layer of graphite
Aka a layer of hexagonal rings of carbon atoms covalently bonded to 3 other carbon atoms
Properties of graphene
Only 1 atom thick
Good conductor of elec
Extremely strong
Why is graphene a good conductor of elec?
Because it is a giant covalent structure
Each carbon atom forms 3 bonds
This means there is 1 delocalised electron per carbon atom
These delocalised electrons can move through the structure carrying a charge
Why is graphene strong?
Not in layers so can’t Slide Over each other
Fullerenes
Molecules of carbon atoms with hollow shapes
Buckminsterfullerene
Contains 60 carbon atoms in hollow sphere
Can have a ring of 5 carbon atoms or 6 carbon atoms
Each bonded 3 times
Fullerenes use
Delivery drugs into the body
Lubricants to reduce friction
Catalysts
Carbon nanotubes
Carbon rings forming a long hollow cylinder
Carbon nanotubes properties
Have high tensile strength
Conduct electricity and heat
Carbon nanotubes uses
Reinforce materials
Polymer vs monomer
The monomer has a double carbon to carbon covalent bond
Whereas the polymer has singular carbon to carbon bonds
Repeating unit
Short hand way of writing a polymer
Has brackets around one section of the polymer (with its single carbon to carbon bond) and an n outside it
The bonds extend outside the bracket
Why are polymers solid at room temperature?
Because the intermolecular forces of attraction between polymer molecules are quite strong
Since they are arranged in layers
It takes a lot of energy to break these many forces
Micrometer
1x10⁻⁶ of a Metre
Nanometre
1x10⁻⁹ of a metre
Coarse particles
Dust
Have a diameter of between 2500 to 10000 nanometres
Contain thousands of atoms
Coarse particles name
PM ₁₀
Fine particles name
PM2.5
Fine particles size
100 to 2500 nanometres
Contain several thousand atoms
Nano particles
Diameter between 1-100 nanometre
Only contain a few hundred atoms
Relationship between particles size and surface area:volume ratio
As it decreases by 10 times
The surface area to volume ratio increases 10 times
Aka the difference gets bigger between surface area and volume increases by x10
Nano particles surface area to volume ratio
Huge because they are the smallest
So have a very large surface area compared to its volume
So we don’t need many of them when using it
Uses of nano particles
Medicine
Suncream
Cosmetics
Deodorant
Electronics
Catalysts
Risks of nano particles
Can be absorbed and enter our cells
Dot and cross diagram
Using dots and crosses to represent the electrons in different atoms when bonding
Advantage of dot and cross diagrams
Clear which electrons belong to which atom and where they are coming from
Stick diagram
Using one line to represent a covalent bond
Stick diagram disadvantage
Don’t tell us which electron came from where/which atom
Don’t tell us about outer electrons not in a bond
Don’t tell us shape of molecule
3d stick diagram
Uses dotted lines and thicker lines to show which bonds are closer and what direction
3d stick diagram advantages
Shows shape of molecule
Ball and stick diagram
Used for giant structures
Where balls are ions and the sticks are bonds
Advantage of ball and stick diagram
Shows ions clearly in 3 dimensions
Ball and stick diagram disadvantage
Shows ions as widely spaced but in reality they are packed closely together
Only shows a tiny part so give inaccurate sizing
Space filling diagram
Where the ions are shown as large balls in 3D with no sticks
Advantage of space filling diagrams
Shows how closely ions are packed together
Disadvantage of space filling diagram
Difficult to see how they’re 3D
Only shows a tiny part of the lattice = inaccurate sizing
Disadvantage of a dot and cross diagram
Don’t tell us the shape of molecule
