1. Formulas and Nomenclature

2. Basic Rules For Writing Formulas
Sum of the charges MUST equal 0 in a neutral compound. (in a polyatomic ion it equals the ions charge)
H20
Positive ion is written first, followed by negative ion
Na+ & Cl- = NaCl
When more than 1 of the same element is in the compound, a subscript is written after the element (no paranthesis)

3. Oxidation number = ion’s charge Monatomic ion = ion with only one atom
When more than 1 polyatomic ion is in a compound, the ion is enclosed in a parenthesis and the subscript follows
Mg+2 & NO3- = Mg(NO3)2
Ion = a charged atom
Oxidation number = ion’s charge
Monatomic ion = ion with only one atom
Polyatomic ion = ion with more than one atom

4. Oxidation number for a free element is zero (normal atom)
There are 7 diatomic elements that occur as pairs when in a pure state O2, N2, I2, H2, F2, Cl2, Br2
The oxidation # for Hydrogen is usually +1 except in hydrides (group 1 and 2)
The oxdation # of Oxygen is -2 except as a peroxide (with group 1 & 2)

5. Type 1 Binary Ionic Compounds
Binary ionic compounds contain a positive ion (cation)which is always written first in the formula and followed by a negative ion (anion).
(The Type 1 metal present forms only a single cation. This means the metals only has one charge or oxidation state.)

6. Writing Binary Ionic Formulas
Writing Binary Ionic Formulas is very simple. If the oxidation numbers or charges of the ions do not balance each other out, we “criss-cross”.
Example: Na+ S2- (these do not balance!)
Na+ S2- Na2S
(when the charges balance, the formula is complete)
Make sure you simplify the subscripts. It is a ratio that is based on the Lowest common mulitple

7. Type 1– Binary Ionic
Nomenclature Rules for naming binary ionic formulas
1st elements always says its complete name
2nd element drops ending (uses only the root word) and adds an –ide ending
Example: KCl – Potassium chloride

8. Hydrides and peroxides form compounds with group 1 and 2 elememts
Ex:
MgH2 and NaH

9. Type II Binary Ionic Compounds
Type II binary ionic compounds contain metals that have more than one type of cation.
Systematic or stock system
Example: Fe 2+ and Fe3+
Both ions are iron but with different oxidation numbers.

10. Writing formulas for Type II Binary Ionic Compounds
These formulas are written exactly like Type I formulas. If the oxidation numbers do not balance out, you “criss-cross” the charges to form subscripts.
Fe2+ Cl-  FeCl2

11. Type II Binary Ionic Compounds
Nomenclature Rules:
Cation says its full name
Oxidation number is given in Roman numerals after the cation’s name
Anion drops its ending (to the root word) and adds an –ide ending

12. Nomeclature for Type II Binary Ionic Compounds
Examples:
FeCl Iron (II) chloride
Cu3N2 -- Copper (II) nitride

13. You don’t know the “charge” of the cation?
If you do not know the oxidation number of the cation, you can determine the “charge” by doing a little algebra. Determine the charge of the anion, then multiply the anion’s charge by the subscript. Take that number and divide by the cation’s subscript.
This will determine the oxidation number of the cation.

14. Find the charge of Carbon
CaCO3
You know Ca has a +2 charge and O has -2
1(+2)+X+3(-2)=0
X=4

15. Special names for Type II Cations
Some Type II cations have a name using the “old” system as well as the “new system”.
The old system, still widely used, adds to the root or stem of the Latin name of the metal the suffixes –ous and –ic. These represent the lower and higher charges respectively.

16. Old Names for Type II ions
Old System
New System
Fe2+
Ferrous
Iron (II)
Fe3+
Ferric
Iron (III)
Cu+
Cuprous
Copper (I)
Cu2+
Cupric
Copper (II)
Sn2+
Stannous
Tin (II)
Sn4+
Stannic
Tin (IV)

17. Two Polyatomic Ions with “Old System” Names
New System
NH4+
Ammonium
Hg22+
Mercurous
Mercury (I)

18. Writing Ternary Ionic Compound Formulas
Ternary Ionic Formulas are formed with a cation or an anion with two or more elements present. We call these anions POLYATOMIC.
Polyatomic ions may be used with either
Type I or Type II ions.

19. Writing Formulas with Polyatiomic Ions
Formulas are written like Type I or Type II ions. If the oxidation numbers or charges do not balance, you “Criss-Cross”.

20. Writing Formulas with Polyatomic Ions
Examples:
Pb2+ PO43- (the charges do not balance)
Pb2+ PO Pb3(PO4)2
The polyatomic ions is in parentheses whenever a subscript is added.

21. Naming Ternary Ionic Formulas
Nomenclature rules:
The Type I cation says its complete name, Type II cations give charge or use old system of naming
The polyatomic says its complete name

22. Ternary Ionic Compounds
Examples:
PbSO4  lead (II) sulfate
The charge on sulfate is a 2-, therefore the charge on the lead must be a 2+.

23. Type III Binary Covalent Formulas
Type III compounds are nonmetal—nonmetal covalent compounds.
In order to form these compounds, we cannot use charges to predict the formula because the valence electrons are not transferred from one element to another like ionic compounds. These elements share.

24. Binary Covalent Compounds
In order to name the binary covalent compound, we must use prefixes to tell how many of each different element is used in the compound.
You NEVER criss-cross charges with covalent compounds.

25. Greek Prefixes for Covalent Compounds
mono –1
di – 2
tri –3
tetra – 4
penta -- 5
hexa – 6
hepta – 7
octa– 8
nona– 9
deca-- 10

26. Binary Covalent Compounds
Nomenclature rules for Binary Type III compounds:
The first element in compound is named first, using the full element name.
The second element is named as if it were an anion (--ide ending)
Prefixes are used to denote the numbers of atoms present.
The Prefix mono is NEVER used for naming the first element.

27. Naming Binary Covalent Compounds
Example: CCl Carbon tetrachloride
1st element is carbon
2nd element is chlorine (drops –ine and replaces with –ide)
2nd element receives prefix denoting number of chlorine atoms
NOTE: mono was not used with 1st element!

28. Nomenclature continued
Example: N2O – dinitrogen monoxide
1st element says its name
2nd element drops ending and adds –ide
Prefixes are used with both elements to denote quantity in molecule
dinitrogen monoxide (prefixes are underlined only for emphasis)

29. How do I write the formula from the name?
In Type III compounds, writing the formula from the name is very simple. The prefix tells you exactly how many of each element is present.
Example:
Dinitrogen pentoxide N2O5