Ionic Bonding with Polyatomic Ions

Ionic bonding with polyatomic ions

Polyatomic ion – two or more atoms, bonded together, which act like one particle with one charge

Here are six common polyatomic ions, their formulas, and their charges:

- Hydroxide, OH, -1 - Nitrate, NO3, -1 - Carbonate, CO3, -2 - Sulfate, SO4, -2 - Phosphate, PO4, -3 - Ammonium, NH4, +1

(There are many more than this, but these are the most common. Nearly all “polys” are negatively charged. Ammonium is an unusual exception.)

Polyatomic ions

•Within the polyatomic ion, non-metals are bonded covalently to each other.

•However, when the “poly” bonds with a metal, the bond is ionic.

•So, compounds that contain a polyatomic ion can contain both ionic and covalent bonds.

•Polyatomic ions cannot exist by themselves – for example, I can’t show you some nitrate.

They only exist as part of a compound.How do they bond?

They bond exactly the same way as

“monatomic” ions, which we’ve already done.

For example: potassium and oxygen.

As ions, they’re K+1 and O-2, so the formula is K2O. But what if potassium is bonding with sulfate, SO4

-2?

Now you have K+1 and SO4

-2,