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Chemistry help?

post #1 of 27
12/5/10 at 9:01pm
Thread Starter 
I never had any chemistry. I'm working on a project that involves some.

I need to understand what O- means. I know O is oxygen. But I don't know what the + and - things are.

The context is photocatalysis. "Photonic energy catalyses the breaking of ambient oxygen and water vapor molecules into O- and -OH (hydroxyl) molecules." I'm researching hydroxyls, and I've got the intellectual understanding, but not the chemical thing.
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post #2 of 27
12/5/10 at 9:13pm
positive and negative charges
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post #3 of 27
12/5/10 at 9:28pm
Now the only chemistry I've ever had is waht I've picked up in biology classes, BUT I belive what your referring to is a charged atom of oxygen also known as an ion. IT can affect how a compound reacts chemically. Here is a link to info on Ions:

http://en.wikipedia.org/wiki/Ion


I don't think it will greatly affect your research if you don't know the ins and outs of how ions work and how it affects how atoms bond together, but thats for you to decide I hope I helped!
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post #4 of 27
12/5/10 at 10:03pm
Quote:
Originally Posted by LDG View Post
I never had any chemistry. I'm working on a project that involves some.

I need to understand what O- means. I know O is oxygen. But I don't know what the + and - things are.

The context is photocatalysis. "Photonic energy catalyses the breaking of ambient oxygen and water vapor molecules into - and -OH (hydroxyl) molecules." I'm researching hydroxyls, and I've got the intellectual understanding, but not the chemical thing.
Basically, "-" means you have an extra electron, and "+" means you are missing one.
Imagine the molecule of water, for example, you want to break - in vapor
H-O-H, now imagine a set numbers of electrons, who keep the atoms in this molecule together, keep moving back and forth really fast... The whole molecule is neutral, but when you split it, one side will have more electrons, and the other will be missing some (since you don't create electrons) - in this specific case, one side will have one more (marked with "-"), and the other will be missing one (marked with the symbol +).
So, you will be left with H+ OH-.... do I make any sense?
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post #5 of 27
12/6/10 at 7:25am
Thread Starter 
THANK YOU. That's exactly what I needed to know.

Carolina - I think you're right except I think you've got the "+" and "-" backwards. What you wrote makes complete sense - if the "-" means it's missing an electron and "+" means it has an extra one. I know for sure that -OH (hydroxyl radicals) are missing an electron. It's why they're so reactive, and why they're far more oxidative than bleach or hydrogen peroxide, as those contained paired electrons.

I'm also guessing that if the + or - is to the right of the molecule designation, it's an ion, and if it's to the left, it's a radical.
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post #6 of 27
12/6/10 at 7:37am
Quote:
Originally Posted by LDG View Post
THANK YOU. That's exactly what I needed to know.

Carolina - I think you're right except I think you've got the "+" and "-" backwards. What you wrote makes complete sense - if the "-" means it's missing an electron and "+" means it has an extra one. I know for sure that -OH (hydroxyl radicals) are missing an electron. It's why they're so reactive, and why they're far more oxidative than bleach or hydrogen peroxide, as those contained paired electrons.

I'm also guessing that if the + or - is to the right of the molecule designation, it's an ion, and if it's to the left, it's a radical.

I think she had it right. If "-" meant you were missing an electron, that would make it positive. Think about it. If you have something with say, 6 electrons and 6 protons, when one electron is missing you have 6 protons and 5 electrons, making it positive. So, "+" would mean a missing electron. Missing electrons give a positive charge, "+" and extra electrons give a negative charge, "-".
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post #7 of 27
12/6/10 at 7:50am
Thread Starter 
Now that I know how to look it up, I will. But "-OH" is definitely the symbol for an hydroxyl radical, and I know they're missing an electron, and that's also what makes me think that the "-" symbol being on the left indicates a radical as opposed to an ion.
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post #8 of 27
12/6/10 at 8:42am
Could it be that the - is indicating where the rest of the compound binds to the hydroxyl group? I say this because when your writing out a chemical compound you use - to indicate bonds:

http://en.wikipedia.org/wiki/File:Alcohol_examples.gif

Sorry to keep siting Wikipedia but I'm using it to back up what I'm remembering from my classes
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post #9 of 27
12/6/10 at 8:52am
Thread Starter 
Well, I know I'm definitely wrong.

And Danielle, you may be right. Apparently a radical is usually designated as the chemical symbol with a dot after it.



Radicals are: atoms, molecules, or ions with unpaired electrons, and they can have positive, negative, or zero charge.

So I don't know why this one is being written as -OH.

(No wonder I never took chemistry. ).
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post #10 of 27
12/6/10 at 8:56am
Thread Starter 
Oh - and Carolina, you're right about the negative and positive charge.

But apparentaly a radical by definition has one non-paired electron, but it can still (somehow) have a positive, neutral, or negative charge.
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post #11 of 27
12/6/10 at 9:04am
Laurie, I didn't want to put it here.... But I do have a degree in Chemistry I am right
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post #12 of 27
12/6/10 at 10:48am
This is what I'm putting myself in for (Majoring in chemistry )
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post #13 of 27
12/6/10 at 11:22am
Quote:
Originally Posted by Tara & Rob View Post
This is what I'm putting myself in for (Majoring in chemistry )
It is a tough one! I gotta say, it's been many years since I touched anything related to chemistry... 1996 was the last time to be exact! I still see things differently though, that is for sure - 5 years of university, at least that you would hope, right? But I forgot the majority... Man, when I think I studied incredibly hard for soooo long... wow
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post #14 of 27
12/6/10 at 12:00pm
Thread Starter 
So Carolina, what does it mean when the "+" or "-" is BEFORE the chemical abbreviation as opposed to after it?
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post #15 of 27
12/6/10 at 12:31pm
I don't understand ANY of this. LOL No wonder I barely passed Chemistry in high school. The only reason I passed was b/c the teacher didn't want me in his class again. Seriously. Give me Biology any day.
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post #16 of 27
12/6/10 at 12:34pm
Quote:
Originally Posted by LDG View Post
So Carolina, what does it mean when the "+" or "-" is BEFORE the chemical abbreviation as opposed to after it?

Laurie, there is only one possibility: It is the same thing, OR you are looking at a reaction, such as below. BUT if you are looking at this: +H, it is the same as this H+
O2− + H2O → 2 OH−
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post #17 of 27
12/6/10 at 12:57pm
Laurie, one more thing that might make it easier to think about this:
Think about Electrons as electricity, as electric charge... Electrons have the symbol "-".
So, if you have one more electron, you are electrically charged, therefore the symbol "-". If you are missing an electron, your atom is positively charged, therefore the symbol "+".
In our brain, we have the tendency to think more electrons, mark +... But actually, more electrons, means an electric charge, so... "-"!
When you see 2- it means you have two extra electrons floating around that atom or molecule. When you see 2+, means you are missing 2 electrons.
Since atoms and things in nature alike are always looking to be neutral, these ions ("+" and "-") are highly unstable and will react to another "+" or "-".
One "+" will react with a "-" making a neutral molecule... that is the case of H+ + OH- = H2O
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post #18 of 27
12/6/10 at 12:57pm
From what I remember of my most recent chemistry class, and from what I've learned of amino acids in cell biology class- and amino acids all have something called a functional group in their structure, which is what hydroxyl also is, the "-" before the -OH simply indicates the bond that forms whenever OH bonds to another molecule. It can also be written as :OH.
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post #19 of 27
12/6/10 at 1:02pm
Quote:
Originally Posted by ut0pia View Post
From what I remember of my most recent chemistry class, and from what I've learned of amino acids in cell biology class- and amino acids all have something called a functional group in their structure, which is what hydroxyl also is, the "-" before the -OH simply indicates the bond that forms whenever OH bonds to another molecule. It can also be written as :OH.
Well, if it is a long line, yes, but the "+" wouldn't make sense in this case...
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post #20 of 27
12/6/10 at 1:10pm
Yea, it would make absolutely no sense if there is a + before, but I just wanted to throw it out there since she said she's researching hydroxyls and maybe that's what's confusing her. I meant a long line, I just couldn't find it on my keyboard lol..
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post #21 of 27
12/6/10 at 2:12pm
Thread Starter 
Mariya, that's it. The hydroxyl functional group. The radical is written with the dot (it appears it can go before or after).

I really appreciate the help, everyone!
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post #22 of 27
12/6/10 at 2:18pm
Thread Starter 
Wait - the original question was about the oxygen. So basically O- is an electrically charged oxygen molecule? It is missing an electron? (The hydroxyl radical "stole" it?)
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post #23 of 27
12/6/10 at 2:24pm
Quote:
Originally Posted by LDG View Post
Wait - the original question was about the oxygen. So basically O- is an electrically charged oxygen molecule?Yes It is missing an electron?No, it has an extra electron (The hydroxyl radical "stole" it? )
............................
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post #24 of 27
12/6/10 at 2:55pm
Quote:
Originally Posted by LDG View Post
Wait - the original question was about the oxygen. So basically O- is an electrically charged oxygen molecule? It is missing an electron? (The hydroxyl radical "stole" it?)
Also... on your original question:
Quote:
The context is photocatalysis. "Photonic energy catalyses the breaking of ambient oxygen and water vapor molecules into O- and -OH (hydroxyl) molecules.
You are breaking down two different molecules - Water H-O-H, and O-O (Oxygen), so that's why you are getting both negative O-- and OH-; they are not coming from the same molecule... They are coming form different ones... they did not "steal" the electrons from each other, what you are reading is part of their respective molecules.
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post #25 of 27
12/6/10 at 3:28pm
Quote:
Originally Posted by Carolina View Post
It is a tough one! I gotta say, it's been many years since I touched anything related to chemistry... 1996 was the last time to be exact! I still see things differently though, that is for sure - 5 years of university, at least that you would hope, right? But I forgot the majority... Man, when I think I studied incredibly hard for soooo long... wow
I actually chose it because it was a tougher major than biology (seems everyone and their brother has a degree in biology). Hoping it will net me some good $. I already work in the environmental chemistry field - hoping some of the clients will appreciate my many years of experience + a degree when I'm finally done. Got a list of local companies that might have better paying jobs! I've already been in the field 4 years, I'm figuring at least another 6 before my Bachelors is done.
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post #26 of 27
12/6/10 at 4:04pm
Thread Starter 
Quote:
Originally Posted by Carolina View Post
Also... on your original question:

You are breaking down two different molecules - Water H-O-H, and O-O (Oxygen), so that's why you are getting both negative O-- and OH-; they are not coming from the same molecule... They are coming form different ones... they did not "steal" the electrons from each other, what you are reading is part of their respective molecules.
Thanks! I'll muddle through this somehow.
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post #27 of 27
12/6/10 at 4:06pm
Quote:
Originally Posted by LDG View Post
Thanks! I'll muddle through this somehow.
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