In This Lesson:
Unit 3
Ionic
Nomenclature
and Polyatomic
Ions
(Lesson 1 of 4)
Today is Friday (!),
th
October 9 , 2015
Stuff You Need:
Periodic Table
Paper Towel
Pre-Class:
Can you name these compounds?
H2O
CO2
NaCl
HCl
Today you will need your periodic tables that show the
charges for transition metals. You also need a small
paper towel for you and your partner.
Pre-Class Deux
• Can you name these compounds?
– O2
• Oxygen gas
– O3
• Ozone gas
– CO
• Carbon monoxide
– H2SO4
• Sulfuric Acid
Today’s Agenda
• Namin’ stuff.
– In today’s case, ionic compounds and polyatomic
ions.
• Where is this in my book?
– P. 254 and following…
By the end of this lesson…
• You should be able to name ionic compounds,
including those with polyatomic ions.
Quick Reminders
• A compound is a chemical combination of two
or more elements (like the pre-class ones).
• Subscripts indicate how many atoms of an
element are present.
– H2O = 2 Hydrogen, 1 Oxygen
– CO2 = 1 Carbon, 2 Oxygen
• Note that subscripts only apply to the letter
next to them (unless there are parentheses).
Quick Reminders
• Chemists don’t write ones.
– Na+ has a charge of 1+.
– Cl- has a charge of 1-.
– K2S has one sulfur atom.
Quick Reminders
Charge (1-)
Nd2
Subscript (2 Nd atoms)
Quick Reminders
• For elements whose symbols have two letters
(or even three), only the first letter is
capitalized.
– For example, Cobalt is abbreviated Co.
– If you write CO, another person might think it’s a
compound of Carbon (C) and Oxygen (O).
• That’s carbon monoxide!
• Both are deadly, but don’t confuse them.
Quick Reminders
• Remember that cations are positively-charged
ions, and anions are negatively-charged.
– Most cations are metals; some polyatomic ions.
• Example: Ca2+, NH4+
– Most anions are nonmetals; many polyatomic
ions.
• Example: Cl-, SO42-
Cations and Anions
• And since cations
and anions attract
one another…
• They form ionic
bonds, making
ionic compounds.
Need to Know Information
• Now, to name any compound or derive its
formula, you need to know:
– What kind of elements are involved?
• Metal, nonmetal, or metalloid.
– How many elements are there?
• 2 – binary compound
• 3 – ternary compound (usually has a polyatomic ion)
– Are there polyatomic ions?
Wait…polyatomic?
• Polyatomic ions are (usually) small compounds
that behave as one ion.
– In other words, there’s more than one element, but
they act as one. Poly-atomic…get it?
• You should memorize as many of these as
possible.
– Yes, really.
• Here’s a hint:
– Anything ending in “-ide,” except Hydroxide, Peroxide,
and Cyanide, will be found on the periodic table.
– Everything else is on the polyatomic ion charts.
Polyatomic Ion List
• I will give you a list of polyatomic ions, but I assure
you that studying/memorizing the list will be
extremely helpful.
– Note: You will not have a polyatomic ion list on the final.
• Also helpful will be the following slide that shows how
many of the names for polyatomic ions are
determined.
• Important Note:
–
–
–
–
–
“Hydrogen carbonate” is the same as “Bicarbonate.”
“Hydrogen sulfite” is the same as “Bisulfite.”
“Hydrogen sulfate” is the same as “Bisulfate.”
Acetate is more commonly written as C2H3O2-.
Chloride (Cl-) is NOT a polyatomic ion. Just cross it out.
Most Common Polyatomic Ions
These are worth memorizin’!
•
•
•
•
•
•
•
•
Acetate (C2H3O2-)
Carbonate (CO32-)
Chlorate (ClO3-)
Hydroxide (OH-)
Nitrate (NO3-)
Phosphate (PO43-)
Sulfate (SO42-)
Ammonium (NH4+)
Naming Polyatomic Ions
• There’s a system to how these polyatomic ions
are named.
• It’s not the most helpful, but getting a little
familiar with this might be useful.
• Let’s take a look…
Naming Polyatomic Ions
Main Ion
ClO3Chlorate
CO32Carbonate
PO43Phosphate
NO3Nitrate
SO42Sulfate
BrO3Bromate
Naming Polyatomic Ions with Chlorine
Anion
Name
Number of
Oxygen Atoms
Cl
Chloride
0 – “-ide”
ClO-
Hypochlorite
ClO2ClO3ClO4-
Chlorite
1 – “hypo…ite”
(2 fewer than main)
2 – “ite”
(1 fewer than main)
Chlorate
Perchlorate
3 – “ate”
(main ion)
4 – “per…ate”
(1 more than main)
Naming Polyatomic Ions
No O
-2 O
-1 O
Main Ion
+1 O
ClChloride
ClOHypochlorite
ClO2Chlorite
ClO3 –
Chlorate
ClO4Perchlorate
STAR WARS!
(not real)
CO32Carbonate
PO33Phosphite
PO43Phosphate
NO2Nitrite
NO3Nitrate
SO32Sulfite
SO42Sulfate
BrO2Bromite
BrO3Bromate
P3Phosphide
N3Nitride
N2O22Hyponitrite
S2Sulfide
BrBromide
BrOHypobromite
BrO4Perbromate
Time for some practice!
• Polyatomic Ion Puzzle
– The puzzle is like dominoes - match the names of
polyatomic ions to their formulas.
• Note that some sides may not be used.
• Some ions are represented more than once.
• Try many possibilities – don’t give up!
– HINTS:
• There are four obvious corner pieces.
• Cyanide, chromate, dichromate, hydrogen carbonate,
and permanganate only have one match each.
• It’s a 4x4 grid.
Now that that’s over…
• Let’s make sure we know how to predict ionic
charges a little more specifically.
Group 1
Group 1: Lose 1 electron to form 1+ ions
H+
Li+
Na+
K+
Group 2
Group 2: Lose 2 electrons to form 2+ ions
Be2+
Mg2+
Ca2+
Sr2+
Ba2+
Group 13
Group 13:
Ga3+
Al3+
B3+
Group 13: Lose 3 electrons to form 3+ ions
Group 14
Group 14:
Group 14: Rarely form ions
Group 14
Group 14:
Ge4+
Sn4+
Pb2+
Group 14: 4+ or 2+ ions
Group 15
N3- Nitride Group 15: Gain 3 electrons to form 3- ions
P3- Phosphide
As3- Arsenide
Group 16
Group 16:
O2- Oxide
Group 16: Gain 2 electrons to form 2- ions
2S Sulfide
Se2- Selenide
Group 17
Group 17:
IBrFCl-
Iodide
Bromide
Fluoride
Chloride
Group 17: Gain 1 electron to form 1- ions
Group 18
Group 18:
Group 18: Noble gases do not form ions
Hey, wait a sec…
• By now you may be thinking, “But Mr.
G…didn’t you forget the transition metals?”
• No. I did not. Chill.
– They’re just weird.
Transition
Metals
Groups 3 - 12:
Transition Metals: Many transition metals
2+ = Iron (II)
Fe
have more than one oxidation state
Fe3+ = Iron (III)
Multivalent Elements
• For transition elements (and some others), things
can get tricky.
• Most have either 1 or 2 valence electrons.
• Some have more or less.
• Some have more than one amount of valence
electrons.
– These are called multivalent metals because they
have multiple valence numbers (charges).
• They are often written as this:
– Element (charge written as Roman numeral)
Common Multivalent Elements
• Copper (Cu) – either 1 or 2 valence electrons.
– Copper (I) or Copper (II) – 1+ or 2+
• Nickel (Ni) – either 2 or 3 valence electrons.
– Nickel (II) or Nickel (III) – 2+ or 3+
• Iron (Fe) – either 2 or 3 valence electrons.
– Iron (II) or Iron (III) – 2+ or 3+
• Lead (Pb) – either 2 or 4 valence electrons.
– Lead (II) or Lead (IV) – 2+ or 4+
• Tin (Sn) – either 2 or 4 valence electrons.
– Tin (II) or Tin (IV) – 2+ or 4+
• Mercury (Hg) – either 1 or 2 valence electrons.
– Mercury (I) or Mercury (II) – 1+ or 2+
However…
• Some transition elements have only one
possible oxidation state.
– Zinc (Zn) – Zn2+
– Silver (Ag) – Ag+
Valence Electrons and
Multivalent Metals
• How many valence electrons does Iron (I)
have?
– One.
• If it forms a +1 charge, it must have one electron to give
up.
• How many valence electrons does Lead (IV)
have?
– Four.
• If it forms a +4 charge, it must have four electrons to
give up.
Nomenclature
• Before we begin nomenclature, I’m going to
hand out a flowchart to everyone.
• Treat this piece of paper like it’s a piece of
solid Au, or Pt.
– Get it?
• Anyway, this paper will save you a lot of
frustration. Trust me.
Nomenclature
• We now reach something called nomenclature,
which is a fancy name for a very particular
naming system.
– Ain’t that a coincidence?
Nomenclature
• When naming ionic compounds (that’s today’s
lesson), cations’ names are not changed.
– In other words, a sodium ion is called a “sodium ion.”
• Anions, however, are referred to by the element
stem followed by –ide.
– Chlorine becomes chloride, nitrogen becomes nitride,
fluorine becomes fluoride (becomes toothpaste).
• Thus, NaCl is called “sodium chloride,” not
“sodium chlorine” or “sodide chloride” or
whatever.
Procedure
• To name ionic compounds, follow these four steps:
1. Write the symbols for the cation and anion, including
charges. Put polyatomic ions in a circle. Do not
change anything in the circle.
2. Check to see if the charges are balanced (=0).
3. Balance charges, if necessary, using subscripts.
4. If you need more than one of a polyatomic ion, use
parentheses at the end. ONLY for polyatomics!
• Simplify subscripts, remove circles and charges to clean it all
up.
Remember the Goal
• Your goal is to make sure that the positive
parts of the compound are completely
balanced with the negative ones.
– In other words, the overall charge adds to 0.
Quick Reminder
Charge (1-)
Nd2
Subscript (2 Nd atoms)
Example: Iron (III) chloride
1. Write the symbols for the cation and anion,
including charges.
2. Check to see if the charges are balanced (=0).
3. Balance charges, if necessary, using subscripts.
– Clean it up (and don’t leave a space).
Fe3+Cl-
3
Total Positive
Charge
3+
Not
balanced!
Total Negative
Charge
13-
Example: Barium nitrate
1. Write the symbols for the cation and anion, including
charges. Put polyatomic ions in a circle.
2. Check to see if the charges are balanced (=0).
3. Balance charges, if necessary, using subscripts.
4. If you need more than one of a polyatomic ion, use
parentheses. ONLY for polyatomics!
– Clean it up.
Ba2+ ( NO3- )2
Total Positive
Charge
2+
Not
balanced!
Total Negative
Charge
12-
About Parentheses
• Parentheses make a difference only when you have
multiple polyatomic ions.
• Imagine if you need multiple pairs of shoes. You want
two sets of shoes, not just two left shoes.
• Similarly, (OH)2 says you want two sets of OH.
• However, OH2 says you want water and wrote it
backward.
• Parentheses don’t make a difference if it’s just an
atom or one polyatomic ion.
– You write Cl2, not (Cl)2.
– (NO3)3 or (OH)2 are not the same as N3O9 and OH2.
Example: Ammonium sulfate
1. Write the symbols for the cation and anion, including
charges. Put polyatomic ions in a circle.
2. Check to see if the charges are balanced (=0).
3. Balance charges, if necessary, using subscripts.
4. If you need more than one of a polyatomic ion, use
parentheses. ONLY for polyatomics!
– Clean it up.
( NH4+) SO422
Total Positive
Charge
2+
1+
Not
balanced!
Total Negative
Charge
2-
Example: Aluminum sulfide
1. Write the symbols for the cation and anion,
including charges.
2. Check to see if the charges are balanced (=0).
3. Balance charges, if necessary, using
subscripts.
– Clean it up.
Al3+ S2-
2
Total Positive
Charge
3+
6+
3
Not
balanced!
Total Negative
Charge
26-
Alternative Method: The Cross-Over
23+
Al S
2
3
Cross-Over Weaknesses
Beware!
• Try doing calcium sulfide using the cross-over
method.
– Wrong: Ca2S2
– Right: CaS
• Reason? The charges were already balanced.
• Try doing germanium oxide using the crossover method.
– Wrong: Ge2O4
– Right: GeO2
• Reason? Always simplify the subscripts if possible.
Example: Magnesium carbonate
1. Write the symbols for the cation and anion,
including charges. Put polyatomic ions in a
circle.
2. Check to see if the charges are balanced (=0).
– Clean it up. Remember to simplify.
Mg2+ CO32Total Positive
Charge
2+
Are balanced!
Total Negative
Charge
2-
Example: Zinc hydroxide
1. Write the symbols for the cation and anion, including
charges. Put polyatomic ions in a circle.
2. Check to see if the charges are balanced (=0).
3. Balance charges, if necessary, using subscripts.
4. If you need more than one of a polyatomic ion, use
parentheses. ONLY for polyatomics!
– Clean it up.
Zn2+ ( OH-)2
Total Positive
Charge
2+
Not
balanced!
Total Negative
Charge
21-
Example: Aluminum phosphate
1. Write the symbols for the cation and anion,
including charges. Put polyatomic ions in a
circle.
2. Check to see if the charges are balanced (=0).
– Clean it up.
Al3+ PO43Total Positive
Charge
3+
Are balanced!
Total Negative
Charge
3-
Practice
• To practice all this stuff, let’s turn to the
Nomenclature Practice Sheet worksheet, first
page.
• Try the first section (1-12).
Now let’s do all that again. Backwards.
• You’ve now learned how to write the formula
of an ionic compound from its name.
• Now let’s take the formula of an ionic
compound and write its name.
Binary Compounds
• Binary compounds are those with two
elements.
– Example: CaCl2
• For these, first write the cation:
– Calcium
• Then write the anion root (chlor–) with the
suffix –ide.
– chloride
• Calcium chloride!
Binary Compounds
• What’s the name of NaCl?
– Sodium chloride
• Al2O3
– Aluminum oxide
• AlN
– Aluminum nitride
Binary Compounds
• What’s the name of MgI2?
– Magnesium iodide
• AlCl3
– Aluminum chloride
• Na3P
– Sodium phosphide
Binary Compounds
• Remember there are some elements that are
multivalent.
• For these, you need to specify which charge
that particular ion is carrying (in parentheses).
– Do this by figuring out the negative charge and
working backward to find the cation charge.
• Example on the next slide…
Binary Compounds
with Multivalent Elements
• What is the name of PbCl2?
• Well, we know it’s Lead (___) chloride, but we
need to figure out the kind of lead we have.
– Lead could be 4+, 2+, or possibly something else.
• To figure that out, let’s start with Chlorine.
– Two chlorines each show up to this party, each with a
1- charge. Total charge? 2-.
• With one Lead atom balancing this out, the Lead
must be Lead (II).
– Lead (II) chloride!
Binary Compounds
with Multivalent Elements
• What’s the name of PbO2?
+4 -4
PbO2
– Lead (IV) oxide
• Mn2O3
– Manganese (III) oxide
+6 -6
Mn2O3
• CuCl2
+2 -2
CuCl2
– Copper (II) chloride
• Ti(Cr2O7)2
– Titanium (IV) dichromate
+4
-4
Ti(Cr2O7)2
Ternary Compounds
• Some compounds, like that last one, contain
more than two elements.
• Ternary compounds contain three.
– They often include polyatomic ions.
• Naming works the same way.
• The trick is to know when you’re looking at a
polyatomic ion.
– How do you know? There will be a total of more
than two elements there!
Ternary Compounds
• NaNO3
– Sodium nitrate
• Fe2(SO4)3
– Iron (III) sulfate
• Cesium perchlorate
– CsClO4
• Ammonium phosphate
– (NH4)3PO4
• Calcium hydroxide
– Ca(OH)2
Practice
• To practice all this stuff, let’s turn to the
Nomenclature Practice Sheet worksheet, first
page.
• Try the second section (13-24).
Takeaways
• Roman numerals tell you the charge of an
atom, NOT how many there are.
– Subscripts tell you how many atoms there are.
• Roman numerals are used only for cations that
make multiple charges.
– Also, they are only used in names, not formulas.
• Parentheses are used only when you need
more than one of a polyatomic ion.
– Never around a single element.
It’s time to play…
• Fix That Ionic Compound!
• I’ll give you a name and a formula.
• Your job is to fix the part that is in bold text.
Fix That Ionic Compound!
Corrections
• Potassium sulfide is K2S1
– K2S
• BaI2 is barium iodine
– Barium iodide
• SrBr2 is strontium (II) bromide
– Strontium bromide
• Titanium (IV) oxide is Ti(IV)O2
– TiO2
Fix That Ionic Compound!
Corrections
• CuCl2 is copper chloride
– Copper (II) chloride
• The lead in PbO2 has a charge of 2+
– 4+
• Magnesium oxide is Mg2O2
– MgO
• Sodium nitrate is Na3N
– NaNO3
Fix That Ionic Compound!
Corrections
• There are 4 phosphate molecules
in AlPO4
–1
• Ca(CN)2 is calcium carbon nitride
– Calcium cyanide
• Strontium hydroxide is SrOH2
– Sr(OH)2
• Ammonium chlorite is NH4(ClO2)
– NH4ClO2
Closure
• Remind me what the name of this ion is: Cl– Chloride
• And do you know what HCl is?
– Hydrochloric Acid
• Remind me what polyatomic ion this is: SO42– Sulfate
• And do you know what H2SO4 is?
– Sulfuric acid
• Any pattern here?
Closure Part Deux
• What’s the name of this compound? CO2
– Carbon dioxide
• And what’s the name of this compound? CO
–
–
–
–
Hint: It’s toxic but odorless and colorless.
Double Hint: You probably own a detector for it.
Triple Hint: It’s not smoke.
Carbon monoxide.
• What’s up with that? Why isn’t it “carbon oxide?”
– Hint: Location on the table?
– Double Hint: Metal or nonmetal?
Extra Practice
• For extra practice, turn your Nomenclature
Practice Sheet worksheets face down and try
#1-20.