What is a polyatomic ion?
A polyatomic ion is simply a collection of covalently bound atoms, with a formal excess or deficiency of electrons......... Nitric acid is a NEUTRAL species, and we could draw the Lewis Structure as.....
Around the leftmost oxygen atom, there are 6 valence electrons, and 2 inner core electrons..... And thus with 2 inner shell electrons (i.e. the
For sulfate, we have a similar distribution......
And for ammonium, we have a quaternized nitrogen,
Just to add that for the purposes of assigning formal charge, we can go back to very old ideas that we learn when are introduced to bonding. In a covalent bond, electrons ARE SHARED between nuclei. An ionic bond is between a formal anion, and a formal cation, and thus involves the prior TRANSFER of electron.
If we take say methane, with FOUR
Likewise, the carbon atom claims 4 electrons from the four
A polyatomic ion is a charged chemical species with more than one type of atom present.
Polyatomic ions are used worldwide on a daily basis, some common ones being nitrate (
Polyatomic ion species often bond chemically with metals to create simple ionic compounds, consisting of a geometric array of ions.
You'll be using polyatomic ions throughout your chemistry career, so it wouldn't hurt to know a bunch of them by memory; here is a list of some polyatomic ions:
Don't stress yourself trying to memorize them, a lot comes with experience and using them over and over!
An important thing to know about polyatomic ions is that they are (most of the time) considered as individual species during chemical reactions. That is to say, most of the time they will remain in that form during a chemical reaction, and won't transform into another substance.
Here's an example:
Suppose you're mixing a solution of
The chemical reaction is
This is a precipitation reaction, one in which a very low-soluble ("insoluble") salt is formed in aqueous solution.
As you can see, the polyatomic ion
The preciptation of
Keep in mind this was just an overview of the basics of what polyatomic ions are, and I don't expect this to be your sole source of information, but maybe some extra information you originally din't get.