C3 Bonding Flashcards
What is ionic bonding?
The TRANSFER of electrons with a METAL AND NON METAL.
This creates a strong bond with strong electrostatic forces
What does a dot and cross diagram show?
Explain?
Covalent compouds
You draw 2 atoms woth there electrons either being dots or corsses (1 for each element)
You can then draw these again but with the extra electron changing atom
Name some ionic compouds?
MgO
MgCl_2
Na_2O
What are the benifits of a dot and cross diagram?
It is simple
It shows the change in the compoud
What are the disadvantages of a dot and cross diagram?
They don’t show the structure of the coupound
They arn’t to scale
What is the structure of an ionic compoud?
Giant ionic lattice
This is a regular lattice structure
What is a giant ionic lattice?
A closely packed regular lattice which is connected by ionic bonds. This means that the electrostatic forces holding the lattice together are really strong. This means that it has a high melting and boiling point
It is made up of oppositly charged ions in all directions of the lattice
What are the similar properties of an ionic compound?
They have a high melting and boiling point due to the strong electrostatic forces. Lots of energy are needed to break these
They can’t conduct electricity when they are a solid but when they are in a liquid they will conduct electricity
Some ionic compounds disolve in water. The ions will seperate and will be free to move around. This means that they will conduct electricity
How do you work out the empirical formula of an ionic compound from a diagram or from a dot and cross diagram?
Dot and cross diagram
Count the electrons to find out what element they are
And look at how many of each element there are
DIAGRAM
Look at the amount of electrons each element would need to get to a charge of 0
Balnce them
Eg
K (potassium) forms 1+ ions
O (oxygen) forms 2- ions
You would need 2 K atoms to make the overal charge 0
Therefore the empirical formula is K_2O
What is covalent bonding?
When non metal’s share electrons to complete there outer shells
This can also happen in non metal compounds
Are covalent bonds strong or week?
Why?
They are strong
The electrons are attracted to both of the positivly charged nuclei. This creates strong electrostatic bonds
How do you draw a dot and cross diagram for covalent bonding?
They outer shellss of the electrons need to be overlaping
There will be pairs of electrons inside the shared area
There will be the same amount of crosses as dots in each overlap
What is a displayed formula
Explain it?
When you draw lines to show the covalent bonding - 1 line = 1 bond …
What are the advantages of a displayed formula?
Shows how the atoms are connected in large molecules
What are the disadvantages of a displayed formula?
It is 2D
It doesn’t show where the covant bond comes from
What is the 3D model / ball and stick model?
Explain it?
A way of showing covalent bonds
It is a 3D representation
What are the advantages of the ball and stick model?
You can see the gaps between the bonds
Easy to use
You can see how the atoms are arranged
What are the disadvantages of the ball and stick model?
It can get very confusing with larger covalent structures
They don’t show where the electrons have come from
It isn’t to scale
What are simple molecular structures?
Substances that are made out of a few atoms joined by covalent bonding
Give some common examples of common simple molecular structures?
H_2
Cl_2
N_2
O_2
CH_4
H_2O
HCl
What are the properties of simple molecular structures?
To boil / melt them you don’t need to break the strong covalent bonds (between the atoms) but the very week intermolecular forces between each molecules (each H_2 molecule). Therefore the MELTING AND BOILING points are LOW
Most simple molecular substances are liquid or gas at room tempreture
As the molecules get bigger the strength of the intermolecular forces increase so the melting and boiling points increase
They don’t conduct electricity because they don’t have a free electron or ion
What is a polymer?
Long chains of repeating units which form long molecules by covalent bonds
How do you draw a poleymer?
Using straight lines (to show the covalent bonds)
Showing the shortest repeated chain (this is called the POLY(ETHENE)
Enclosed by brackets around the bit that repeates
Some of the covalent binds may extend outside the brackes to show that is repeates
The letter n on the bottom right of the brackets that shows that it repeats a lot of times
What are some charatristics of polymers?
The intermolecular forces between polymers are larger than the covalent bonds between simple covalent molecules. Therefore they have a higher melting point/ boiling point that simple covalent molecules.
Thye are normally a SOLID at room tempreture
The intermolecular forces are still normally weeker than ionic bonds therefore they have a lower melting point / boiling point that ionic compounds and giant molecular compounds
What are macromolecules?
A structure which has a lot of atoms in it
What are giant covalent structures?
Give 3 examples?
They are macromolecules
All atoms are bonded to each other with strong covalent bonds
Diamond, graphite, silicon dioxide
What are some charatristics of giant covalent structures?
They don’t conduct electricity (other than a few exceptions such as graphite).
Even when they are in a molten form
What is metalic bonding?
The sharing of delocalised electrons between 2 or more metals
What is the structure of metal?
Giant structure
They contain delocalised electrons in there outer shell (this means they are free to move around)
When metals share these they create powerfull metalic bonds
The delocalised electrons create strong electrostatic attraction between the positive metal ions and the negative electrons
What substances can metalic bonding make?
Alloys
Metalic elements
What are the charatristics of most metals?
Most metels are soild at room tempretures
The electrostatic forces between the metals are very strong and they require a lot of energy to break. This leads to a high metling and boiling point
Theu conduct electricity and heat well
Are malluable (this means they can be bent, hammered or rolled into flat sheets easily)
All charatristics are because of the delocalised electrons
Why are alloys harder than pure metals?
Alloys are a mixture of different sized metal atoms. This means that they layers won’t slide over each other easily because the layers have been DISTORTED. This makes it harder for the layers to slide over each other whuch makes the metal harder.
