POLYATOMIC IONS
Two or more atoms covalently
bonded, the resulting particle has a
charge.
Many polyatomic ions are listed on the back of your
periodic table.
Other polyatomic ions are on page 224 of your
textbook.
Look at the list on the back of your periodic table.
When the polyatomic ion has a negative one charge, it
wants to gain one electron.
On your worksheet, list the polyatomic ions that want to
gain one electron.
What would be the charge of a polyatomic ion
that wants to gain 2 electrons?
-2
Now find the polyatomic ion with a positive
charge, it is called ammonium.
NH4+1
The positive charge means it wants to lose an
electron.
Let’s look at sulfate…
An atom of sulfur has 6 valence electrons.
An atom of oxygen also has 6 valence electrons.
When you put 4 oxygen atoms with 1 sulfur atom,
you get a structure that looks like this……
Notice how the one oxygen does not have a complete octet, it wants to gain two
more electrons for an octet. This is why the sulfate ion has a negative 2 charge.
Practice
When given a formula, you know it contains a polyatomic ion if it
has more than 2 elements. Use your periodic table and write the
name of the following on your worksheet.
ZnCO3
NaNO3
K2SO4
NH4Br
Practice
Hopefully you got the following:
ZnCO3
NaNO3
K2SO4
NH4Br
Zinc(II) carbonate
Sodium nitrate
Potassium sulfate
Ammonium bromide
Practice a few formulas
Lithium phosphate
Aluminum carbonate
Barium hydroxide
Iron(III) acetate
Hopefully you got these:
Lithium phosphate
Aluminum carbonate
Barium hydroxide
Iron(III) acetate
Li3PO4
Al2(CO3)3
Ba(OH)2
Fe(C2H3O2)3