AQA Chemistry Unit 1 - 13th January

Dative convalency
Drawing shapes of molecules and a similar ion (remember brackets and charge on ion)
Bonding and structure of iodine, water, ice, diamond, graphite, NaCl (probably two of these)
Mole calculations
Ideal gas equation rearranging
Definition of ionisation or detection or deflection in mass spectrometry
Calculating the Mr of an element from mass spectrometry values
Definition of relative atomic mass/molecular formula/empirical formula
Empirical formula calculation
Bonding of H2O between 2 molecules (or HF)
Combustion equation
Explain a trend in ionisation energies for a given period, name one atom that deviates from trend
Link size of Van der Waals forces to boiling points somehow

I would post my chemistry teacher over to you but I don't think he'd fit in an envelope. :P

I found this:
http://www.chemguide.co.uk/atoms/bonding/shapes.html
Bit wordy but goes through the basics.

Simple thing to do is this:

Look at the group number eg. Nitrogen = 5

Look how many things it is bonded to: eg. NH3 = 3.

Add these numbers eg 5+3=8.

Divide this by two to get the number of PAIRS eg 8/2=4.

4 Would mean the electron arrangement is a tetrahedral shape.

Since there are 3 bonding pairs (NH3) there is one lone pair.

. .
N
/ | \
H H H

That is what it would look like with a lone pair at the top This shape is pyramidal.

That help at all?

AQA GCE AS Chemistry Unit 1.

http://web.aqa.org.uk/qual/gce/science/chemistry_noticeboard.php?id=03&prev=03

I hate diamond and graphite for some reason i just cant put it into words
when they usually ask like the structure and bonding of diamond and / or graphite, whats the model answer?

Thanks but i am a little confused
Can you please tell me if the paper you are talking about consists only of multiple choice questions.
I have Chemistry tomorrow too Edexcel GCSE Board and I assume that's a different one? Right?

Diamond:
BONDING is covalent - shared pairs of electrons
STRUCTURE is macromolecular
PROPERTIES - very high melting point, strong because very many very strong covalent bonds require a lot of heat (only for melting) energy to break
Doesn't conduct electricity because all 4 outer energy level electrons are used in bonding so electrons cannot move

Graphite:
BONDING is covalent - shared pairs of electrons
STRUCTURE is macromolecular
PROPERTIES - very high melting point, strong THROUGH LAYERS because very many very strong covalent bonds require a lot of heat (only for melting) energy to break
BUT weak between layers because only weak forces between layers requires little energy to overcome, so layers can slide over each other.
Does conduct electricity because only 3 outer energy level electrons are used in bonding so electrons can move between layers, so when voltage is applied, electrons move in the same direction.



Yep, Edexcel is a different board.
Nothing is multiple choice on our paper.

I am aware that 4s comes before 3d
Just wondering whether to actually right 4s before 3d?
I've seen some exam questions that do but seen some that don't?
What do you guys do?

So chromium is [Ar] 4s1 3d5, and then first ionisation leads to Cr+ [Ar] 3d5??? please correct me if im wrong

Another thing to add to the answer above..

in diamond, each carbon is bonded to 4 other carbons whereas in graphite its bonded to 3 other carbons....so therefore diamond has a higher melting point also, as more bonds need to be broken.

hope i helped

do we need to know that??

btw any possibilities on what might come up tomorrow

thank you so much!!!!!
ill be sure to memorise that incase it comes up

Lol just did Jan 09 again - the last question is basically about cars LOL

I hate it when common sense questions like that come up. -____________-

Dative convalency
Drawing shapes of molecules and a similar ion (remember brackets and charge on ion)
Bonding and structure of iodine, water, ice, diamond, graphite, NaCl (probably two of these)
Mole calculations
Ideal gas equation rearranging
Definition of ionisation or detection or deflection in mass spectrometry
Calculating the Mr of an element from mass spectrometry values
Definition of relative atomic mass/molecular formula/empirical formula
Empirical formula calculation
Bonding of H2O between 2 molecules (or HF)
Combustion equation
Explain a trend in ionisation energies for a given period, name one atom that deviates from trend
Link size of Van der Waals forces to boiling points somehow

Iodine and water are just known as "molecular" structures right?

yup thats right..

diamond, graphite, silicone are macromolecular...but diamond and graphite and macromolecular crystals

Yep knew about those three - how different is silicon to diamond?