How can OH be negative if O and H are covalently bonded?

[danne89]

Hi!
In a molecule, let's say NaOH, the Na is a positive ion and the OH a negative one. How can a molecule, OH, be negative. The binding between the O and the hydrogen is, I think, colvalent. But doesn't that mean that the OH-group is charged? And how can that group binds to the other and be NaOH?

 

[dextercioby]

Hi!
In a molecule, let's say NaOH, the Na is a positive ion and the OH a negative one. How can a molecule, OH, be negative. The binding between the O and the hydrogen is, I think, colvalent. But doesn't that mean that the OH-group is charged? And how can that group binds to the other and be NaOH?

It is negative souly to the fact that one of the unpaired electrons from the oxygen atom is not hooked up in any bond.The other one is hooked up with the electron from the H atom in a covalent bond.
So basically,OH has an unpaired electron,which means a "-" net charge.What u call "molecule",is actually a radical,molecules,IIRC are electrically neutral...

Daniel.

 

[danne89]

Can you develop your last sentence; I don't get it, maybe because me English sucks.

This's kind of new to me. Can you redirect me to a good website (yes, I've checed the Chemestry Napster).

 

[Gokul43201]

He is saying that $OH^-$ is not a molecule. To be a molecule, it has to be electrically neutral.

 

[danne89]

What's it then. My teacher's saying it's stable and can exist freely.

 

[The Bob]

If I am correct, it would be a negative ion.

The Bob (2004 ©)

 

[Gokul43201]

What's it then. My teacher's saying it's stable and can exist freely.

It is stable, and can exist freely (under certain conditions - such as in an equeous solution). But that doesn't make it a molecule. To be a molecule, it must be neutral.

It is referred to as a 'radical' or ion. In this case, it is a negatively charged radical, with 1 excess electron.