Gabzinc
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What?

So I was doing revision for end-of-year exams, and came across this question:

5 Which of the following statements about the elements in Group 7 is incorrect?

A. They all show variable oxidation states in their compounds.
B. They all form acidic hydrides.
C. Electronegativity decreases as the group is descended.
D. They all exist as diatomic molecules.

I thought the correct answer is D, because Astatine is not diatomic (as far as I know, but I've also checked the internet), and Chlorine can be involved in disproportionation reactions eg in the reaction with water and with cold/hot alkali...

Apparently though, the answer is A.

Could anyone clear things up for me and explain why? Thanks.
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Pigster
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(Original post by Gabzinc)
What?

So I was doing revision for end-of-year exams, and came across this question:

5 Which of the following statements about the elements in Group 7 is incorrect?

A. They all show variable oxidation states in their compounds.
B. They all form acidic hydrides.
C. Electronegativity decreases as the group is descended.
D. They all exist as diatomic molecules.

I thought the correct answer is D, because Astatine is not diatomic (as far as I know, but I've also checked the internet), and Chlorine can be involved in disproportionation reactions eg in the reaction with water and with cold/hot alkali...

Apparently though, the answer is A.

Could anyone clear things up for me and explain why? Thanks.
Fluorine is only ever F- in compounds. Don't bother reading the other oens. It is the most electronegative, nothing is going to oxidise it.

D is contentious, there is evidence for and against the existence of diatomic At.

I'm not sure why you mention disproportionation.
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Gabzinc
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(Original post by Pigster)
Fluorine is only ever F- in compounds. Don't bother reading the other oens. It is the most electronegative, nothing is going to oxidise it.

D is contentious, there is evidence for and against the existence of diatomic At.

I'm not sure why you mention disproportionation.
Hmm... I thought disproportionation would disprove the fact the chlorine only has one oxidation state, because it could also have a +1 (HClO) and +5 (NaClO3) oxidation state? But then again flourine is always -1 so I guess that doesn't disprove A.

I guess by deduction the answer is indeed A, but if there isn't concrete evidence suggesting that Astatine is diatomic then I wonder why it's a question. :/ Damn Edexcel.
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Pigster
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(Original post by Gabzinc)
then I wonder why it's a question. :/ Damn Edexcel.
I don't know Edexcel, but is it required knowledge to know that At isn't diatomic?
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