Naming Ionic Compounds

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Transcript Naming Ionic Compounds

Naming Ionic Compounds
Monatomic Ions
Made from a single atom gaining or losing an
electron (based on valence electrons)
Element
Oxidation #
+1
Li
+2
Be
-2
O
-1
F
 Writing ions- write symbol, write charge as
a superscript
Ex. Al+3

Writing Ionic Compounds
Made of two parts – cation & anion
 Name the cation first (typically a metal)
just as it appears on periodic table
Na+  Sodium
Ca+2  Calcium

Writing Ionic Compounds with
Transition Metals
Most transition metals have more than
one oxidation number
 If the transition metal has more than one
oxidation number, you must represent it
with a Roman Numeral in its name

Transition Metals to know
Scandium column – always +3, no Roman
Numeral needed
 F-block – always +3, no Roman Numeral
needed
 Ag – always +1, no Roman Numeral
needed
 Cd & Zn – always +2, no Roman
Numeral needed

Transition Metals to know (cont.)
Sn & Pb – either +2 or +4
 Sn & Pb and all other transition metal’s
oxidation # will be determined by
“uncrossing the criss-cross”
(I’ll explain in a minute)
Examples:
Fe+2  Iron II
Fe+3  Iron III
Al+3  Aluminum Cu+2  Copper II
Cu+  Copper I Zn+2  Zinc

Writing Ionic Compounds (cont.)
Write the anion next (typically a
nonmetal)
 Change the ending to –ide
Cl- , chlorine  chloride
O-2 , oxygen  oxide
**If the anion is a polyatomic ion, the name
stays the same**

Writing Ionic Compounds Practice
NaCl
FeS
AlCl3
Na2O
Al2O3
CuO
Sodium Chloride
Iron II Sulfide
Aluminum Chloride
Sodium Oxide
Aluminum Oxide
Copper II Oxide
How to determine the Oxidation
Number of Transition Metals
Identify metal as a Transition with multiple
oxidation numbers
 Uncross the “criss-cross”
 If nothing to uncross, identify the charge
of the anion (they will always only have
one oxidation number), charges have been
simplified
 Transition metal charge is the same as
anion charge (just +)

How to determine the Oxidation
Number of Transition Metals (cont.)
Ex. #1
Fe2O3
+3
-2
Fe2O3
Iron III Oxide
How to determine the Oxidation
Number of Transition Metals (cont.)
Ex.#2
FeS
**No subscripts to show charge, so ID
anion charge
 S = -2, therefore Fe must be +2
 Name = Iron II Sulfide
Ex.#3
CuO
 Name = Copper II Oxide
Writing an Ionic Formula
Identify the charge on each part of the
compound (cation and anion)
 Remember…the sum of the oxidation
numbers MUST EQUAL ZERO
 Add subscripts to balance charges (can be
done with criss-cross method)

Writing an Ionic Formula (cont.)
Ex. #1 = Calcium Chloride
Ions  Ca = +2
Chlorine = -1
+2
-1
Ca
Cl
Formula = CaCl2
(Remember…never write 1’s)
Writing an Ionic Formula (cont.)
Ex.#2 = Magnesium Oxide
Ions  Mg = +2
O = -2
Use “criss-cross”  Mg2O2
**Simplify when possible  MgO
Extra Rule
Can’t change a Polyatomic Ions subscripts
(if you need multiple polyatomics, you
must put the ion symbol in brackets)
Ex. PO4 = has a -3 charge
Ca = has a +2 charge
Formula = Ca3(PO4)2

Changes to Polyatomic Ions
We must know the “root” polyatomic ion
(the ones on our list)
 Oxygens can either be added or
subtracted from the formula we know
 When that happens, the polyatomic ion
name changes

Changes to Polyatomic Ions (cont.)
1 more oxygen  per-ate
Root

-ate
1less oxygen 
-ite
2 less oxygens  hypo-ite
**the charge remains the same**
Ex. SO5 = Persulfate
SO4 = Sulfate
SO3 = Sulfite
SO2 = hyposulfite