1. Ionic Compounds Naming and Writing Formulas
Chemistry II
Ionic Compounds
Naming and Writing Formulas

2. Review of how ions are formed
Octet rule – elements are most stable when they have 8 valence electrons
Elements can gain or lose valence electrons in order to have 8.

3. Formation of Cation sodium atom Na sodium ion Na+ 11p+ 11p+ e- e- e-
loss of
one valence
electron
11p+ e- e- e- e- e- e-

4. Formation of Anion chlorine atom chloride ion Cl1- Cl 17p+ 17p+ e-
gain of
one valence
electron e- e- e- e- e- e- e- e-
17p+ e- e- e- e- e- e- e- e- e- e-

5. Bonding
Chemical Bond
attractive force between atoms or ions that binds them together as a unit
Purpose bonds formFORM IN ORDER TO ….
To decrease potential energy (PE)
To Increase stability
Atoms in all substances that contain more than one atom are held together by electrostatic interactions—interactions between electrically charged particles such as protons and electrons.
Courtesy Christy Johannesson

6. Why bonds form…
Atoms of many elements are more stable as they are bonded to other atoms.
Energy is released into surroundings resulting in a system with lower energy.
An atom’s electron configuration determines how it interacts with other atoms
Particularly valence electrons

7. What are ionic bonds?
Chemical interactions(attractions) between charged particles - Called Electrostatic attraction
Result from a transfer of electrons making a cation and anion

8. Crystal Lattice NaCl 1:1 Ratio
Strong Attractions within a crystal lattice.
Remember the atoms transfer the electrons and then are attracted to each other because of opposite charges
Ionic compounds do not exist as single molecules but rather as numerous units organized in a stable crystal .

9. Participants Ionic bonds form between metals and non-metals
Metals have lower ionization energies and therefore more readily “give away” electrons – Form Cations
Non-metals have high electron affinities and therefore more readily accept electrons. – Form Anions
New Term- Oxidation Number = ion charge
sodium’s oxidation number is 1+, Chlorine’s is 1-

10. Naming Ionic Compounds
Cation – borrows name from element
Always listed first
Anion – ends in “ide” (with the exception of polyatomic ions)
Always listed second
Examples
NaCl – sodium chloride
ZnS – zinc sulfide
Mg3N2 – magnesium nitride
SPELLING COUNTS!

11. Example: Aluminum Chloride
Writing Ionic Formulas
Criss-Cross Rule
Example: Aluminum Chloride
Step 1:
Write symbols & charge of elements.
Write charges ABOVE the letters
Al Cl 3+ 1-
Step 2:
Al Cl
criss-cross charges as subscripts 1 3
Step 3: AlCl 3
combine as formula unit
*“1” is never shown
*get rid of charges on top
Step 4 : *simplify if needed

12. Variable Charge Ions
Some elements in the transition metals can form more than one type of ion. Sometimes they may lose 2, 3, 4 or even more electrons in order to bond with another element.
So these metals can form +2, +3 ,+4 etc cations in one compound but have a different charge in another compound. In order to tell them apart we name them differently.

13. Writing the formula
When given the name of the compound, the Roman numeral after the metal tells us the CHARGE of the metal.
Copper II Chloride – means Cu+2 Cl-1
Follow the same steps as before >>>>
1. Write out the charges
2. Criss-cross
3. Combine as a formula unit (get rid of charges on top)
4. Simplify if needed

14. A. To name, given the formula:Cu Fe
Figure out charge on
cation.
2. Write name of cation.
3. Write Roman numerals
in ( ) to show cation’s charge.
Stock System
of nomenclature
4. Write name of anion.
FeO
iron oxide
Fe?
Fe2+
O2–
iron (II) oxide
Fe2O3
Fe?
iron oxide
Fe3+
Fe?
Fe3+
O2–
O2–
O2–
iron (III) oxide
CuBr
copper bromide
Cu?
Cu1+
Br1–
copper (I) bromide
CuBr2
Cu?
copper bromide
Cu2+
Br1–
Br1–
copper (II) bromide

15. When writing the formula for an ionic compound with a polyatomic ion, follow the same rules but treat the polyatomic ion as a single unit.

16. Writing Formulas w/Polyatomic Ions
a group of atoms that stay together and have a single, overall charge.
Ba and SO42–
BaSO4
barium sulfate
Mg and NO21–
Mg(NO2)2
magnesium nitrite
NH41+ and ClO31–
NH4ClO3
ammonium chlorate
Sn4+ and SO42–
Sn(SO4)2
tin (IV) sulfate ?
Fe3+ and Cr2O72–
Fe2(Cr2O7)3
iron (III) dichromate
NH41+ and N3–
(NH4)3N
ammonium nitride

17. Rules for Parentheses There is a (polyatomic ion) present and…
Parentheses are used only when the following
two condition are met:
There is a (polyatomic ion) present and…
There are two or more of that in the formula.
Examples:
NaNO3 NO31- , but there is only one of it.
Co(NO3)2 NO31- there are two of them
(NH4)2SO4 NH41+ there are two of them;
SO42- there is only one of it.
Co(OH)2 OH1- there are two of it.
Al2(CO3)3 CO32- there are three of them.
NaOH OH1- there is only one of it.

18. Pattern to Memorizing NomenclatureXY
“-ide”
XYO4
XYO3
XYO2
XYO
“per___-ate”
“-ate”
“-ite”
“hypo___-ite”
1 more oxygen
normal
1 less oxygen
2 less oxygen

19. Physical Characteristics
Physical characteristics result from the strong attractive forces between charged particles and the crystal structure
High melting and boiling points
Lots of energy necessary to break strong bonds
Solid at room temperature
Stable crystal structure
Hard and brittle
Crystal allows compound to withstand great force
Too much force causes repulsive forces to overpower attractive forces and the crystal shatters
Conduct electricity when melted and dissolved in water
Charged particles that are able to move