IGCSE CHEMISTRY DOUBTS HERE !!!!

[elemis]

1 minute.

[elemis]

12.04/23 = 0.5235

11.52/11 = 1.047

29.32/16 = 1.833

47.12/18 = 2.62

Dividing all the above numbers by the lowest number gives a ratio of : 1 : 2 : 4 : 5

Formula = NaB₂O₄5(H₂O)

hence answer is C

[elemis]

For second one.

Its Ultraviolet rays, they cause sunburn.

[Adzel]

Thanks and +rep!!! 

[Adzel]

Ari or someone can you do this for me plz, I need to check my answers... 

By the way +rep will be given...

[elemis]

Thats going to be hardwork

I'll do question 1

[Adzel]

 please I really need them all...

[elemis]

Nucleus has an overall +ve charge.

2

6

10

The spin will be in opposite directions i.e. one will spin anticlockwise and the other clockwise.

[elemis]

Rutherford Experiment, right ? I'm sure you know this.... its in your textbook probably.

A surprise since 1 in 20000 alpha particles were deflected backwards causing scintillations.

Revised to include a nucleus which contains most of the mass of an atom; though this mass is concentrated in a VERY small area.

Ummm, I think Gold foil was used since gold is very malleable and could be made easily into a thin sheet of foil - remember Alpha particles have a very low penetration.

I guess exposure to radiation used in testing is the answer.

[Adzel]

No. 2 I did it correctly... so carry on to Q3. plz

By the way Thanks for helping...

[elemis]

I have no idea of the answers to Question 3. I've just started my AS Level. SO forgive me

Question 6

a) http://www.periodictable.com/Elements/028/data.html Click on the elements at the top of the page to view the Electronic Config.

b) I dont understand what they are ak

[elemis]

QUestion 5

[elemis]

4 a) The amount of energy needed to remove an electron from one mole of an atom of a gaseous element.

[Ivo]

I have no idea of the answers to Question 3. I've just started my AS Level. SO forgive me

Question 6

a) http://www.periodictable.com/Elements/028/data.html Click on the elements at the top of the page to view the Electronic Config.

b) I dont understand what they are ak

For Question 6) b):

i) The 4s orbital will fill before a 3d orbital, because the 4s orbital is at a lower energy level than a 3d orbital.  The order of filling orbitals based on their energy level is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, ...

ii) It is strange that the 4s orbital has not been completely filled up before moving on to the 3d orbital (which incidently is full - filled with 10 electrons).  This is because copper is one of the exceptions to Hund's rule, where one of the 4s electrons moves into the last 3d orbital.  This is known to be because there is more stability if it is arranged in this way - a full 3d subshell.

iii) Chromium is the other exception, arranged in a similar way - with having a half full 3d subshell, which appear to be associated with greater stability.

[Deadly_king]

For Question 6) b):

i) The 4s orbital will fill before a 3d orbital, because the 4s orbital is at a lower energy level than a 3d orbital.  The order of filling orbitals based on their energy level is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, ...

ii) It is strange that the 4s orbital has not been completely filled up before moving on to the 3d orbital (which incidently is full - filled with 10 electrons).  This is because copper is one of the exceptions to Hund's rule, where one of the 4s electrons moves into the last 3d orbital.  This is known to be because there is more stability if it is arranged in this way - a full 3d subshell.

iii) Chromium is the other exception, arranged in a similar way - with having a half full 3d subshell, which appear to be associated with greater stability.

Hehe......this whole paper was already answered in another thread.

Anyway thanks for the help