Happy_Puppy5000

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Oct 2, 2012
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Hello All:

I believe that I should post this in the Question/Answer section. However, I think I shall post it here.

I have been around for awhile and keep saying that I am going to quit working and get serious and study for the MCAT, but year after year I put it off.

Anyway, yesterday on my way to the local Walmart, I walked quickly into the Barnes & Noble to check what's new in MCAT world. I saw this MC Graw-Hill MCAT practice exam book. So I pick it up and opened it. It opened up to the first C/P section, so I read the first question that I saw. Now below is the question:

Which of the following metals is considered diamagnetic?

A. Ca
B. (I believe was Al)
C. (Don't recall)
D. Cu

I am positive that the answer was Ca. However, before I check I remembered that Cu, Ag, Au (in addition to Cr and Mo) were exceptions to the shell filling rule. Cu 3d shell is filled completely. Nonetheless, that would leave a 4S1 (not 4S2.) In fact, either way Cu would not be diamagnetic. Hence, I placed a one million dollar bet on choice A and went to collect. Some how they say the answer is D. Stating: of the choices Copper is the only diamagnetic metal.

I immediately put that book down and went about the rest of my day. My question is am I wrong (I really don't think so)? Also as anyone used that book as a source of practice? I am thinking that it really can not be any good. However, I am literally basing that on only one question.
 

Lawpy

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Determining whether something's paramagnetic or diamagnetic depends on the state of the element discussed (if it's neutral vs an ion vs a metallic solid). I think your reasoning works if the question is talking about an isolated neutral atom. But the answer choice seems to be talking about elements as metals rather than isolated neutral atoms, and that becomes a different scenario:

Why is copper diamagnetic?

Why is calcium paramagnetic?

Pretty sure the reasons in the above sources are beyond the scope of the MCAT because it requires knowledge of quantum mechanics and advanced inorganic chemistry.

McGraw Hill isn't a commonly used MCAT resource and I probably wouldn't use it.
 
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