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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 17 of 17. This is the beginning of the thread.
Posted by alexandra_k on April 29, 2009, at 13:19:28
So I thought I was getting the difference between ionic / extravalent bonds and covalent bonds but now I'm confused again...
NaCl is an example of an extravalent bond because Sodium DONATES one electron to Clorine to satisfy the octet rule.
H2 is an example of a single covalent bond because two elements of Hydrogen SHARE one electron (one pair of electrons) to satisfy the octet rule.
C02 is an example of a double covalent bond because two elements of oxygen SHARE two pairs of electrons with carbon to satisfy the octet rule.
H20 is an example of a double covalent bond because two elements of Hydrogen SHARE two pairs of electrons to satisfy the octet rule.
But then apparently 'water molecules dissociate continually in a reversible reaction to form hydrogen ions (H+ and hydroxide ions (OH-):H20 <--> H+ + OH-
Hmm.
But then does H2 similarly dissociate continually in a reversible reaction to form hydrogen ions (H+ and H-)?
And then do carbon dioxide molecules dissociate continually in a reversible reaction to form carbon ions and hydrogen ions (C- and 2O+)?
If so... Then I lose the distinction between extravalent bonds and covalent bonds (donating vs sharing).
Does this have something to do with problems locating electrons in clouds?
Is this basically an issue of 'don't worry about it just keep going and learn about carbs / proteins / lipids'?
Posted by alexandra_k on April 29, 2009, at 13:23:55
In reply to chemistry help, posted by alexandra_k on April 29, 2009, at 13:19:28
Isn't it funny how a bunch of bollocks (Bohr's model of the atom) can be so useful?
Maybe I'm missing some kind of hierarchy to do with the strength of bonds or something like that...
Posted by Kath on April 29, 2009, at 18:26:56
In reply to chemistry help, posted by alexandra_k on April 29, 2009, at 13:19:28
It is all Greek to me! As the saying goes!
No friggin' CLUE as to any of it!
LOL you must be one smart cookie.
hugs, Kath
Posted by BayLeaf on April 29, 2009, at 18:32:10
In reply to Re: chemistry help, posted by alexandra_k on April 29, 2009, at 13:23:55
Posted by Deneb on April 29, 2009, at 19:33:21
In reply to chemistry help, posted by alexandra_k on April 29, 2009, at 13:19:28
> So I thought I was getting the difference between ionic / extravalent bonds and covalent bonds but now I'm confused again...
>
> NaCl is an example of an extravalent bond because Sodium DONATES one electron to Clorine to satisfy the octet rule.
> H2 is an example of a single covalent bond because two elements of Hydrogen SHARE one electron (one pair of electrons) to satisfy the octet rule.
> C02 is an example of a double covalent bond because two elements of oxygen SHARE two pairs of electrons with carbon to satisfy the octet rule.
> H20 is an example of a double covalent bond because two elements of Hydrogen SHARE two pairs of electrons to satisfy the octet rule.
> But then apparently 'water molecules dissociate continually in a reversible reaction to form hydrogen ions (H+ and hydroxide ions (OH-):
>
> H20 <--> H+ + OH-
>
> Hmm.
>
> But then does H2 similarly dissociate continually in a reversible reaction to form hydrogen ions (H+ and H-)?No, I have forgotten a lot of basic chemistry, but no, H2 does not dissociate, the bonds are too strong. H- is not possible unless it is an ionic bond with something like NaH. H2 is actually very stable and is a gas.
> And then do carbon dioxide molecules dissociate continually in a reversible reaction to form carbon ions and hydrogen ions (C- and 2O+)?
No, definitely no. The bonds are too strong. Carbon dioxide is a covalently bonded molecule. Two carbon ions are extremely unstable, and I don't think a positively charged oxygen is possible.
>
> If so... Then I lose the distinction between extravalent bonds and covalent bonds (donating vs sharing).
>
> Does this have something to do with problems locating electrons in clouds?
>
> Is this basically an issue of 'don't worry about it just keep going and learn about carbs / proteins / lipids'?
Posted by Larry Hoover on April 29, 2009, at 19:34:07
In reply to chemistry help, posted by alexandra_k on April 29, 2009, at 13:19:28
> So I thought I was getting the difference between ionic / extravalent bonds and covalent bonds but now I'm confused again...
Not so confused as you thought, methinks.
You asked:
"Maybe I'm missing some kind of hierarchy to do with the strength of bonds or something like that... "Precisely so. You're asking just the same questions that were in fact answered by Bohr's theory.
> NaCl is an example of an extravalent bond because Sodium DONATES one electron to Clorine to satisfy the octet rule.
> H2 is an example of a single covalent bond because two elements of Hydrogen SHARE one electron (one pair of electrons) to satisfy the octet rule.Minor correction. Two atoms.
> C02 is an example of a double covalent bond because two elements of oxygen SHARE two pairs of electrons with carbon to satisfy the octet rule.
Again, two atoms of oxygen.
> H20 is an example of a double covalent bond because two elements of Hydrogen SHARE two pairs of electrons to satisfy the octet rule.
Again, atoms.
> But then apparently 'water molecules dissociate continually in a reversible reaction to form hydrogen ions (H+ and hydroxide ions (OH-):
>
> H20 <--> H+ + OH-
>
> Hmm.It would be more understandable, perhaps, if you had the correct equation.
2H20 <--> H3O+ + OH-
The electron octets are retained. Hydrogen ions (H+) are actually quite rare, whereas hydronium ions (H3O+) are not.
> But then does H2 similarly dissociate continually in a reversible reaction to form hydrogen ions (H+ and H-)?Statistically, yes it does. But exceedingly rarely, because the hydride ion (H-) is very reactive.
> And then do carbon dioxide molecules dissociate continually in a reversible reaction to form carbon ions and hydrogen ions (C- and 2O+)?
You've got the polarities backwards, and your signs don't add to zero. But it is once again instability = reactivity that would do these rare forms in with incredible speed.
Superoxide ion is O-, whereas an oxygen atom with a double charge is oxide ion.
The key here to understanding the type of bonds that form is the stability after such a bond has formed.
Sodium metal has one extra electron outside of an octet, so it quite happily rids itself of that electron (explosively donating it to water, for example), leaving it with the stable octet, as Na+ ion.
Chlorine gas is stablized as Cl2, because each atom "borrows" an electron from the other, to form octets. As individual atoms, though, they are stabilized by altogether stealing an electron, to give a full octet, as Cl- ion.
So, chlorine can form stable covalent compounds, or can be stable as a free ion. Ionic bonds are only fractionally as strong as covalent bonds.
> If so... Then I lose the distinction between extravalent bonds and covalent bonds (donating vs sharing).
>
> Does this have something to do with problems locating electrons in clouds?No, that's another property of electrons that doesn't literally influence reactivity.
> Is this basically an issue of 'don't worry about it just keep going and learn about carbs / proteins / lipids'?
No, I think it's better to get this idea settled, so you can build upon it.
I'm happy to help with this.
Lar
Posted by Deneb on April 29, 2009, at 19:39:21
In reply to Re: chemistry help » alexandra_k, posted by Larry Hoover on April 29, 2009, at 19:34:07
Thanks for explaining Larry. I have forgotten a bunch of chemistry. LOL
Your explanation sounds good.
Posted by Larry Hoover on April 29, 2009, at 20:02:11
In reply to Re: chemistry help, posted by Deneb on April 29, 2009, at 19:33:21
> I don't think a positively charged oxygen is possible.
It's an arbitrary distinction, perhaps, but the formal charge on the hydronium ion (H3O+) is on the oxygen atom. When R is not H, the structure is an oxonium ion. O+ atoms can be created, but I don't know of their existence in nature.
Lar
Posted by Phillipa on April 30, 2009, at 0:24:50
In reply to Re: chemistry help » Deneb, posted by Larry Hoover on April 29, 2009, at 20:02:11
All I know is basically nothing except H2O is water two hydrogen atoms and one oxygen molecule. Co2. One Carbon Atom And Two Oxygen Molecules. Does this sound right. One year of chemistry for nursing just started to see it as if can't see things they make no sence like math. Can see 2+2=4. Two sticks on the ground in one place and two more and together it's four. Someone told me years ago and I'm not "street smart" that in NYC 2+2 = 5. But I have found the theory of nines in fourth grade all numbers ultimately lead to nine. Love Phillipa
Posted by alexandra_k on April 30, 2009, at 16:33:18
In reply to chemistry help, posted by alexandra_k on April 29, 2009, at 13:19:28
Thanks guys, stuff to think about. Grading until 4pm Monday... Should get the chance to get to it on Tuesday :-)
Posted by Larry Hoover on April 30, 2009, at 16:38:49
In reply to Re: chemistry help, posted by alexandra_k on April 30, 2009, at 16:33:18
> Thanks guys, stuff to think about. Grading until 4pm Monday... Should get the chance to get to it on Tuesday :-)
Your Tuesday, or our Tuesday?
Heh.
Lar
Posted by alexandra_k on April 30, 2009, at 16:50:47
In reply to Re: chemistry help » alexandra_k, posted by Larry Hoover on April 30, 2009, at 16:38:49
Our Tuesday. I'm in the US.
Posted by Larry Hoover on April 30, 2009, at 17:00:29
In reply to Re: chemistry help, posted by alexandra_k on April 30, 2009, at 16:50:47
I had no idea you were in the U.S.
Lar
Posted by alexandra_k on April 30, 2009, at 17:31:37
In reply to Re: chemistry help » alexandra_k, posted by Larry Hoover on April 30, 2009, at 17:00:29
Yup. But now I gotta grade :-(
I enjoy reading them okay I just hate having to put numbers / letters on 'em :-(
Just gotta do that until Monday afternoon... Then I'm done...
Then some combo of dissertation writing and learning biochem, biophysics, epidemiology, and anatomy / physiology...
Posted by Phillipa on April 30, 2009, at 22:56:39
In reply to Re: chemistry help, posted by alexandra_k on April 30, 2009, at 17:31:37
Then a weekend road trip that I know you will enjoy. Love Phillipa
Posted by alexandra_k on May 6, 2009, at 16:48:38
In reply to chemistry help, posted by alexandra_k on April 29, 2009, at 13:19:28
Thanks guys. Sorry to post and run but... Time really has come for me to move on. Thanks for the help. Doing the combined strategy of working back through and trying to come to a better understanding and progressing forwards as well not letting it bog me down too much. I'll miss you guys. Take care. Don't let the *ssh*l* grind you down.
Posted by Phillipa on May 6, 2009, at 20:18:39
In reply to Re: chemistry help, posted by alexandra_k on May 6, 2009, at 16:48:38
Alex will miss you bunches. Love Phillipa
This is the end of the thread.
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