What does the MCAT mean when it says "Oxygen Gas?"

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johnwandering

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The BR practice tests note that "Oxygen gas is paramagnetic" in its passages (which O2 is not), it seems quite clear that they are referring to O and not O2 when saying "Oxygen gas."

Yet everywhere else, it seems to note Oxygen gas as O2.


I was wondering, is there a convention in atomic chemistry where a "gas" refers to the molecule's monoatomic state?

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The BR practice tests note that "Oxygen gas is paramagnetic" in its passages (which O2 is not), it seems quite clear that they are referring to O and not O2 when saying "Oxygen gas."

Yet everywhere else, it seems to note Oxygen gas as O2.


I was wondering, is there a convention in atomic chemistry where a "gas" refers to the molecule's monoatomic state?

O2 is paramagnetic. "Oxygen gas" = "O2(g)"
 
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I forgot: how do we determine if an atom is diamagnetic or paramagnetic?

Unfilled orbitals (resulting in an unpaired electron within an orbital) = paramagnetic.

All filled = diagmagnetic
 
Unfilled orbitals (resulting in an unpaired electron within an orbital) = paramagnetic.

All filled = diagmagnetic

we consider the oxygen in its elemental form, right. 6 electrons.

not when it is covalently bound = 6 + 2 shared = full p orbital.
 
But when bound, what matters is no longer those p orbitals, but rather the full hybridized molecular orbitals. Those fill in such a way that oxygen has two half-filled molecular orbitals.

http://en.wikipedia.org/wiki/Molecul...gen_MO_diagram

Unfilled orbitals (resulting in an unpaired electron within an orbital) = paramagnetic.

All filled = diagmagnetic


I am not exactly sure what you guys mean... it shouldn't matter if those orbitals are filled or half-filled.
The Only thing that matters in diamagnetic/paramagnetic is if there is an Unpaired electron.

O2 clearly does not have any unpaired electrons... so why is it paramagnetic?

Cl2 has an unfilled orbital, but it is diamagnetic.
 
O2 does have unpaired electrons in the pi orbital. don't look at the structure but look at the periodic table and you will see according to hunds rule, or who ever it was, electrons fill 1 at a time before doubling up in orbitals. O has two unparied electrons. II I I
 
I am not exactly sure what you guys mean... it shouldn't matter if those orbitals are filled or half-filled.
The Only thing that matters in diamagnetic/paramagnetic is if there is an Unpaired electron.

O2 clearly does not have any unpaired electrons... so why is it paramagnetic?

Cl2 has an unfilled orbital, but it is diamagnetic.

O2 does have unpaired electrons.

O2.gif
 
I am not exactly sure what you guys mean... it shouldn't matter if those orbitals are filled or half-filled.
The Only thing that matters in diamagnetic/paramagnetic is if there is an Unpaired electron.

O2 clearly does not have any unpaired electrons... so why is it paramagnetic?

Cl2 has an unfilled orbital, but it is diamagnetic.

^ What they said
 
same thing as oxygen but two more electrons lol

also the lower orbitals are filled before the higher orbitals.
 
Can someone draw Cl2 and show why thats diamagnetic??


It looks like the O2 one shown above except replace 2s and 2p with 3s and 3p and add one "up" arrow in both the pi*3px and pi*3py orbital.

Cl is [Ne]3s^2 3p^5, so Cl2 will have 10 p orbital electrons in the MO diagram.

Fill sigma3p first (2), then pi3p (4), then pi*3p (4) and you used up all 10 of your electrons and have no unpaired electrons.
 
Whoa those MO diagrams

Wait what are antiorbitals?
I thought u couldnt put anything in those or the bond would break...
 
Whoa those MO diagrams

Wait what are antiorbitals?
I thought u couldnt put anything in those or the bond would break...

They are higher energy (unstable) bonds than the bonding orbitals. They exist and since electrons can be anywhere at any given time you must account for them.
 
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