# Hydroxide Ion

1. ### andyrk

583
Why does the hydroxide ion have a negative charge? , i.e OH-?

2. ### DrDu

4,349
Because if not, it would be a hydroxide radical and not an ion?

3. ### ArielRodriguez

6
Think octet rule and lewis dot structures... you need one more electron to make the oxygen stable, so it has a 1- charge.

1,533
The simplest way for explaining this is this:
O2-+H+=(OH)- (It's actually (OH)-)

This is not stable(Stable form is H2O)

Here H+ Cancels out one electron of O2-

So one electron is left.Therefore it is left with a negative charge
-2+1=-1

5. ### Enigman

648
Count the number of protons and number of electron in the ion.
With reference to what Drdu said: ions are charged, radicals are neutral.
chemistry sometimes overcomplicates things to simplify them...

6. ### Yanick

401
Radicals need not always be neutral.

See: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2644638/

Also you can have stuff like the superoxide anion which is a anion radical. See: http://en.wikipedia.org/wiki/Superoxide

Plenty of examples around, these are just off the top of my head.

7. ### Enigman

648
Sorry for not being clearer, I was talking about hydroxyl radicals which DrDu mentioned rather than radicals in general.
As for the definition of radical I believe the only prerequisite is having an unpaired electron/ incompletely filled valence shell and the species in question may be an atom, ion or a molecule.