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Relative atomic mass mass spectra

image.png How do you work out the relative atomic mass? I don't have a clue... Someone please take me through step by step
2a. 2,8,8,8,8,8,8,2
2b.
i.I dont know
ii. different isotopes
you should get a revision guide.
Original post by KnowledgeIsBest
2a. 2,8,8,8,8,8,8,2
2b.
i.I dont know
ii. different isotopes
you should get a revision guide.


Presuming this is an A level paper your answer to 2a would get precisely zero marks out of one every single time.
Original post by MexicanKeith
Presuming this is an A level paper your answer to 2a would get precisely zero marks out of one every single time.


why? and its not an A-level paper, its a GCSE additional science question.
Original post by Lucofthewoods
image.png How do you work out the relative atomic mass? I don't have a clue... Someone please take me through step by step


Relative atomic mass is simply the average of the isotopic masses, each weighted with the abundance of that isotope.

For example Chlorine has two common isotopes
35Cl (~75% abundance) and 37Cl (~25% abundance)
(ie 3/4 of chlorine is 35, 1/4 of chlorine is 37

so the relative atomic mass of chlorine would be

(35 x 3/4) + (37 x 1/4) = 35.5

Hopefully that example might give you an idea how to do this question :smile:
Original post by KnowledgeIsBest
why? and its not an A-level paper, its a GCSE additional science question.


Okay, GCSE additional science, that might be an acceptable answer (struggling to remember back that far!)

The reason it wouldn't get the marks in my book is simply because the question asks for an electron configuration, and a series of numbers is not a configuration.

A configuration would look more like this:

1s22s22p63s23p64s23d104p65s24d105p4

or more simply

[Kr]5s24d105p4

Which will make no sense to most GCSE students.

If the examines were looking for the style of answer you gave then I think this is a rather unfortunate situation where GCSE oversimplifies. Sorry for jumping on your back about your answer!
Original post by KnowledgeIsBest
why? and its not an A-level paper, its a GCSE additional science question.


Just found the paper http://filestore.aqa.org.uk/subjects/AQA-CHEM1-QP-JUN15.PDF

It's A level so your answer is definitely not going to get any marks

also in the question it gives you [Kr] to begin with so it definitely wants the full configuration as I've given above! :smile:

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