Chapter 5 Notes
Names & Formulas for Ionic Compounds
Chemists discuss compounds by using both _____________ _______________ and _______________.
The chemical formula and name must be ______________________ understood.
Formulas for Ionic Compounds
The ________________ ___________ is the simplest ratio of the ions represented in an ionic compound.
Examples of formula units could be KBr, ___________, or ____________. The number of ___________ gained
by the _____________ ______ is equal to the number of __________ lost by the _____________ ______.
A ________________ ________ is a one-atom ion. Examples are _____, _____, or _____. The _____ charge is
determined by its location on the ___________ ___________. The ______________ ____________ is just the
charge of a monatomic ion. Many ________________ ____________ have more than one oxidation number –
meaning they can give away different numbers of electrons to form different compounds.
**Figure 6 on page 163 shows many transitions metals & their common ions.
Cross-Over Method for Determining Ionic Formulas
1. Determine the symbol and oxidation number (charge) for each ion involved in the formula.
2. Start with each ion side by side ** + ion on the left, - ion on the right**
3. Cross the + ion’s charge down to make it the – ion’s subscript (drop the + sign)
4. Cross the – ion’s charge down to make it the + ion’s subscript (drop the – sign)
5. Make sure the formulas subscripts are reduced as much as possible to make it a formula unit.
Example 1: Determine the correct formula for an ionic compound containing sodium and chlorine.
Step 1: Write ions side by side
Na +1
Cl-1
Step 2: Cross charges to get subscripts
Na1Cl1
Step 3: Reduce subscripts to the formula unit
NaCl
Example 2: Determine the correct formula for an ionic compound containing magnesium and phosphorus.
Step 1:
Mg
P
Step 2:
Mg P
Step 3:
Mg P
Example 3: Determine the correct formula for an ionic compound containing calcium and nitrogen.
Step 1:
Step 2:
Step 3:
Example 4: Determine the correct formula for an ionic compound containing potassium and tellurium.
Step 1:
Step 2:
Step 3:
Compounds That Contain Polyatomic Ions
A _________________ ______ is an ion made up of more than one atom. The __________ given to a
polyatomic ion applies to the entire group of ____________, not just the last element in the formula! The
polyatomic ion acts as an __________________ ____________. The rules for writing formulas containing
polyatomic ions are _______________ ________ ___________ as formulas containing only monatomic ions.
** Table 2 on page 178 shows common polyatomic ions and their formulas.
We will have a 15 point BONUS quiz on the following ions on THURSDAY, MARCH 5:
Ammonium, Nitrate, Nitrite, Hydroxide, Permanganate, Chlorate, Chlorite, Acetate, Carbonate, Sulfate,
Sulfite, Peroxide, Chromate, Dichromate, and Phosphate – 1 point each
**You must know the formulas and the names in order to receive credit – no partial credit will be given**
Example 1: Determine the correct formula for an ionic compound containing sodium and sulfate.
Step 1: Write ions side by side
Na+1
SO4+2
Step 2: Cross charges to get subscripts
Na2(SO4)1
Step 3: Reduce subscripts to the formula unit
Na2SO4
Example 2: Determine the correct formula for an ionic compound containing beryllium and chromate.
Step 1:
Be2+
CrO42Step 2:
Be (CrO4)
Step 3:
Be CrO4
Example 3: Determine the correct formula for an ionic compound containing potassium and nitrate.
Step 1:
Step 2:
Step 3:
Naming Ions and Ionic Compounds
An ____________________ is a polyatomic ion composed of an element, usually a nonmetal, bonded to one
or more _____________ atoms. Many ___________________ contain the same ______________ and have
the same ________________ but differ in the number of ________________ atoms. More than one oxyanion
exists for some _________________ (ex. nitrogen and sulfur). Use the following for naming such oxyanions.
 The ion with _____________ oxygen atoms has the suffix –ate (ex. Sulfate, SO42-)
 The ion with _____________ oxygen atoms has the suffix –ite (ex. Sulfite, SO32-)
Naming Ionic Compounds
1. Name the cation first and the anion second.
2. Name the monatomic metal cation with just the element’s name.
3. Name the monatomic non-metal anion by adding –ide to the root name of the element.
4. If the metal cation is a transition metal, it could have multiple oxidation numbers – if so, write the
name of the cation followed by a Roman numeral to represent the charge - ex. Fe3+ becomes iron (III)
**This is known as the Stock Naming System
5. If the compound contains a polyatomic ion, simple name the polyatomic ion.
Example 1: Name the following ionic compound: NaCl
Step 1:
cation: sodium
anion: chloride
Step 2:
metal cation is not a transition metal, so no Roman numeral is needed
Step 3:
does not contain a polyatomic ion
Step 4:
Sodium Chloride
Example 2: Name the following ionic compound: Cs3N
Step 1:
cation: cesium
anion: nitride
Step 2:
metal cation is not a transition metal, so no Roman numeral is needed
Step 3:
does not contain a polyatomic ion
Step 4:
Cesium Nitride
Example 3: Name the following ionic compound: Cu3N2
Step 1:
cation: copper
anion: nitride
Step 2:
copper is a transition metal, must determine if copper (I) or copper (II)
Step 3:
does not contain a polyatomic ion
Step 4:
Copper (II) Nitride
Example 4: Name the following ionic compound: LiNO3
Step 1:
cation: lithium
anion: nitrate
Step 2:
metal cation is not a transition metal, so no Roman numeral is needed
Step 3:
does contain polyatomic ion – NO3 is nitrate
Step 4:
Lithium Nitrate
You name the following ionic compounds: MgCl2, MnP, Ca(ClO3)2, Na3PO4, Fe2(SO3)3, and Sn(SiO3)2