AQA AS Chemistry, unit 1

I'm doing this on Thursday too :biggrin:

Can anyone explain the difference in the second and first ionisation energies...

I just generally don't get it :s-smilie:

Reply 24

Chewy29

6

Original post by gooner1886

If I remember the question correctly it does say it's pretty much life graphite? And that it has a high melting point and conducts electricity?

Just write down what you would do for graphite i.e. Macromolecular, has very strong bonds, these strong bonds must be overcome/broken, which requires a high amount of heat energy.

Conducts electricity because it has layers with delocalised electrons between them which allow current to flow.

okay. Thankyou :smile:

Reply 25

lucysmorley

Original post by gooner1886

If I remember the question correctly it does say it's pretty much life graphite? And that it has a high melting point and conducts electricity?

Just write down what you would do for graphite i.e. Macromolecular, has very strong bonds, these strong bonds must be overcome/broken, which requires a high amount of heat energy.

Conducts electricity because it has layers with delocalised electrons between them which allow current to flow.

It's on the june 2012 past paper if you want to check :smile:

Reply 26

Paulineuh

Original post by x-Sophie-x

I'm doing this on Thursday too :biggrin:

Can anyone explain the difference in the second and first ionisation energies...

I just generally don't get it :s-smilie:

First IE - you're removing the outer e- from a neutral atom e.g. A = atom
A(g) --> A+(g) + e-
On the left is the neutral atom, on the right is what is formed - a positive ion with the charge +1 and one e-

Second IE - you're removing the next e- after the one you've just removed so from a positive (+1) ion.
A+(g) --> A2+(g) + e-
Left: Positive ion
Right: What is formed when you remove another e- from the positive ion.

Hope that kinda made some sense :3 Bad at explaining lol :colondollar:

Reply 27

Original post by Paulineuh

First IE - you're removing the outer e- from a neutral atom e.g. A = atom
A(g) --> A+(g) + e-
On the left is the neutral atom, on the right is what is formed - a positive ion with the charge +1 and one e-

Second IE - you're removing the next e- after the one you've just removed so from a positive (+1) ion.
A+(g) --> A2+(g) + e-
Left: Positive ion
Right: What is formed when you remove another e- from the positive ion.

Hope that kinda made some sense :3 Bad at explaining lol :colondollar:

Oh no I understand that, sorry :colondollar:

Thank you anyway :h:

What I meant was, I don't understand those questions where they ask why the second ionisation energy of sodium is say lower than the first ionisation energy of magnesium or something like that..

Reply 28

Original post by x-Sophie-x

I'm taking this exam for the first time. Because our stupid school insists we get better results if we do both units in the summer Urgh! :angry:

I hate periodicity the most :frown:

Periodicity Summarised for you :smile:

Period 3:
Atomic Radius:

•

Decreases across period

•

Due to more and more protons in nucleus/increasing nuclear charge

•

Electron shielding stays constant

Melting/Boiling Points:

•

Increases from Na-Al due to stronger and stronger metallic bonds (explain)

•

Silicon has highest MP/BP in period 3 because it is a giant covalent structure

•

Sulfur has a greater MP/BP than Phosphorus because Sulfur exists as S8 and Phosphorus exists as P4

•

van der Waals attraction increases in strength with size

•

Phosphorus has a higher MP/BP than Chlorine for same reason (Cl2)

1st IE:

•

General trend is for the exact same reasons as atomic radius except this time it is increasing rather than decreasing

•

Al has a lower 1st IE than Mg because it's outermost electron is in the 3p subshell which is further away than the 3s subshell where the outermost electron of Mg lies

•

This means the outermost electron of Al is further away from the nucleus than Mg's outermost electron so will be easier to remove

•

Sulfur has a lower first IE than Phosphorus because in Phosphorus each of the three 3p orbitals have only one electron in them

•

In sulfur one of the 3p orbitals contains two electrons

•

The repulsion between these two electrons makes it easier to remove one

That is pretty much all you need to know in terms of content for periodicity. However AQA expect you to be able to apply this knowledge to other situations. They may ask about other periods or 2nd/3rd ionisation energies so make sure you understand these principles. Hope that helped :smile:

(edited 10 years ago)

Reply 29

Original post by Sharif Chowdhury

Periodicity Summarised for you :smile:

Period 3: Atomic Radius:

•

Decreases across period

•

Due to more and more protons in nucleus/increasing nuclear charge

•

Electron shielding stays constant

Melting/Boiling Points:

•

Increases from Na-Mg due to stronger and stronger metallic bonds (explain)

•

Silicon has highest MP/BP in period 3 because it is a giant covalent structure

•

Sulfur has a greater MP/BP than Phosphorus because Sulfur exists as S8 and Phosphorus exists as P4

•

van der Waals attraction increases in strength with size

•

Phosphorus has a higher MP/BP than Chlorine for same reason (Cl2)

1st IE:

•

General trend is for the exact same reasons as atomic radius except this time it is increasing rather than decreasing

•

Al has a lower 1st IE than Mg because it's outermost electron is in the 3p subshell which is further away than the 3s subshell where the outermost electron of Mg lies

•

This means the outermost electron of Al is further away from the nucleus than Mg's outermost electron so will be easier to remove

•

Sulfur has a lower first IE than Phosphorus because in Phosphorus each of the three 3p orbitals have only one electron in them

•

In sulfur one of the 3p orbitals contains two electrons

•

The repulsion between these two electrons makes it easier to remove one

That is pretty much all you need to know in terms of content for periodicity. However the AQA expect you to be able to apply this knowledge to other situations. They may ask about other periods or 2nd/3rd ionisation energies so make sure you understand these principles. Hope that helped :smile:

That was extremely helpful. Thank you!

Reply 30

NabRoh

11

Could someone explain to me how shells are filled up using Indium as an example?
Does the 4th shell have an f block (14?)?

So if we went up to the 6th shell would it be:

1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 ...

What comes next?

Reply 31

Original post by x-Sophie-x

That was extremely helpful. Thank you!

You're welcome. I made a teensy mistake in the Melting/Boiling points part. The MP/BP increases from Na to Al not Na to Mg. My apologies :colondollar:

Reply 32

Original post by Sharif Chowdhury

You're welcome. I made a teensy mistake in the Melting/Boiling points part. The MP/BP increases from Na to Al not Na to Mg. My apologies :colondollar:

A very very teensy mistake haha.

Reply 33

Original post by NabRoh

Could someone explain to me how shells are filled up using Indium as an example?
Does the 4th shell have an f block (14?)?

So if we went up to the 6th shell would it be:

1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 ...

What comes next?

5s2 4d10 5p1

There aren't f blocks yet. At least thats what I think :smile:

(edited 10 years ago)

Reply 34

NabRoh

11

Original post by x-Sophie-x

5s2 4d10 5p1

There aren't f blocks yet. At least thats what I think :smile:

So the 4th Shell goes up to D orbitals? Do you know what the 5th one goes to?
I saw the f-block thing when looking for answers on Wikipedia,

Reply 35

Original post by NabRoh

Could someone explain to me how shells are filled up using Indium as an example?
Does the 4th shell have an f block (14?)?

So if we went up to the 6th shell would it be:

1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 ...

What comes next?

4f doesn't come into play until after 6s :smile:

Reply 36

electronic configuration.jpg40.1KB

Original post by NabRoh

Could someone explain to me how shells are filled up using Indium as an example?
Does the 4th shell have an f block (14?)?

So if we went up to the 6th shell would it be:

1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 ...

What comes next?

Here's a picture illustrating the order in which electron subshells fill. Sorry for my bad paint skills xD
Learn how to draw this diagram and you'll never forget the order of subshells.

Reply 37

Original post by Sharif Chowdhury

Here's a picture illustrating the order in which electron subshells fill. Sorry for my bad paint skills xD
Learn how to draw this diagram and you'll never forget the order of subshells.

Wow that is some confusing diagram.

I remember the subshells by just looking at the periodic table and counting along..

Reply 38

Original post by NabRoh

So the 4th Shell goes up to D orbitals? Do you know what the 5th one goes to?
I saw the f-block thing when looking for answers on Wikipedia,

Yep. If you look at a periodic table and count along, it will make things a lot clearer :smile:

The 5th one has d orbitals as well. No F orbitals yet.
We dont need to know about f orbitals in unit 1 chemistry :tongue:

Reply 39