DAT Destroyer GC Problem #244

[sacapuntas]

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I don't understand question 244 from 2011 DAT Destroyer Gen Chem.

It is a question where you have to chose which statement is false.

The answer given is E which states:

e) The strontium cation is larger than the sulfur anion since negative ions gain electrons

The explanation says Sr++ is smaller than S-- since it forms a positive ion. Choice E is clearly False.

I would understand this question if it asked you to decide between Ca++ and S--, but Sr is 2 rows below Sulfur with more than double the mass and protons. Is there any way the cation being positive could make it smaller than an anion with less than half the weight?

It seems like a mistake to me...

What do you think?

 

[Saiph]

The Strontium ion is larger because it is [Kr], while S-- is [Ar]. If it was Ca+2, the S-- will be larger because Calcium lost electrons therefore reducing it's atomic radius.

The answer to your question is no. You just have to look at which noble gas the ion is in, and if the noble gas in a lower period, it is larger in atomic radius.

Edit-Oh wait, sorry just saw that the "answer" is a false answer. Yeah it should be a mistake!

 

[Ferferi]

Guess you're right. I remember I chose this answer correctly by mistake!
Seems like Destroyer assumes that cations are smaller than anions in general.Which is wrong.