1. 7-1: Chemical Names and Formulas
Explain the significance of a chemical formula
Determine the formula of an ionic compound formed between two given ions
Name an ionic compound given its formula
Using prefixes, name a binary molecular compound from its formula
Write the formula of a binary molecular compound given its name

2. Significance of a Chemical Formula
Chemical formula: indicates the relative number of atoms of each kind in a chemical compound
For a molecular formula: gives the number of atoms of each element contained in a single molecule of the compound
Ex: hydrocarbon octane
C8H18
Subscript indicates there are 8 atoms of carbon in a molecule of octane
Subscript indicates there are 18 atoms of hydrogen in a molecule of octane

3. Al2(SO4)3 For an ionic compound: represents one formula unit
Formula unit = simplest ratio of the compound’s positive and negative ions
Ex: aluminum sulfate
Al2(SO4)3
Note: parentheses are used to identify polyatomic ion as one unit
Subscript 2 refers to 2 aluminum atoms
Subscript 4 refers to 4 oxygen atoms in the sulfate ion
Subscript 3 refers to everything inside the parentheses giving 3 sulfate ions, with a total of 3 sulfur atoms and 12 oxygen atoms

4. Monatomic Ions Monatomic ion: ions formed from a single atom
Ex: Na+ , Mg2+ , S2- , N3-
By gaining or losing electrons, many main-group elements form ions with noble-gas configurations
Ex:
Group 1 lose one electron to give 1+ cation
Group 2 lose two electrons to give 2+ cation
Group 15, 16, 17 form anions
Not all main-group elements readily form ions
Ex: carbon & silicon form covalent bonds
d-block elements form variable charges
Copper can be Cu+ or Cu2+
Iron can be Fe2+ or Fe3+
Lead can be Pb2+, Pb3+, or Pb4+

5. Naming Monatomic Ions Positive ions (cations) Negative ions (anions)
Name of element + cation
Ex: K+ Potassium cation Mg2+ Magnesium cation Al3+ ________________ Sr2+ ________________
Negative ions (anions)
Base of element + -ide ending
Ex: F- Fluoride N3- Nitride O2- ________________ Br- ________________
Aluminum cation
Strontium cation
Oxide
Bromide

6. Binary Ionic Compounds
Binary compounds: compounds composed of two different elements
The total # of positive charges and negative charges must be equal
The formula can be written given the identities of the compound’s ions
Ex: Ions combined = Mg2+ , Br- , Br- Chemical formula = MgBr2

7. Writing formulas for ionic compounds: (Ex: Aluminum bromide)
1. Write the symbols for the ions (cations first)
Al O2-
2. Cross over the charges as subscripts Al O3 3. Check to make sure total charges are equal.
Al2O3
Calcium sulfide
Ca2+ S2-
Ca2S2
CaS
2 x (+3) = +6
3 x (-2) = -6

8. You Try!
Write the formulas for the binary ionic compounds formed between the following elements:
1. Potassium and iodine KI
2. Magnesium and chlorine
MgCl2
3. Sodium and sulfur
Na2S
Pg. 205 = common monatomic ions

9. Naming Binary Ionic Compounds
Nomenclature: naming system
Nomenclature of binary compounds involves combining the names of cations and anions
Name cation first, followed by the name of the anion
Ex: Al2O3
1. Name cation first: full name of cation
Aluminum
2. Name anion last: base of anion + -ide
Oxide
Al2O3 = aluminum oxide

10. You Try!
Name the binary ionic compounds indicated by the following formulas:
1. AgCl
Silver chloride
2. ZnO
Zinc oxide
3. CaBr2
Calcium bromide

11. The Stock System of Nomenclature
Some elements form two or more cations with different charges
Use stock system of naming (usually with d-block elements)
Roman numeral represents charge in parentheses
Fe2+ Fe3+
Iron(II) Iron(III)
Ex: Cu2+ + Cl CuCl2
Name of cation Name of anion + Roman numeral indicating charge
copper(II) chloride
Some cations that commonly form only one cation
No anions form more than one charge

12. You Try!
Write the formulas and give the names for the following ionic compounds:
1. Cu2+ and Br-
CuBr2 ; copper(II) bromide
2. Pb2+ and Cl-
PbCl2 ; lead(II) chloride
3. Fe3+ and O2-
Fe2O3 ; Iron(III) oxide

13. Compounds Containing Polyatomic Ions
All but NH4+ (ammonium ion) are negatively charged
Most are oxyanions
Oxyanion: polyatomic ions that contain oxygen
Ex: NO3- –nitrate NO2- –nitrite
Most common anions have –ate endings
Anion with one less oxygen has –ite ending
Anion with two less oxygen has hypo prefix and –ite ending
Anion with one extra oxygen has per prefix and –ate ending
Ex: ClO3- ClO2- ClO- ClO4- chlorate chlorite hypochlorite perchlorate

14. Naming Compounds with Polyatomic Ions
Same as naming for ionic compounds except:
Name polyatomic ion as one unit
Ex:
AgNO3 silver nitrate
Use parentheses if more than one polyatomic ion present
Al2(SO4)3 aluminum sulfate

15. You try! Name the following binary compounds: 1. Na2CO3 2. Ag3PO4
Sodium carbonate
2. Ag3PO4
Silver phosphate
3. FeSO4
Iron(II) sulfate

16. Naming Binary Molecular Compounds
Recall: Unlike ionic compounds, molecular compounds are composed of individual covalently bonded units, or molecules
Two nomenclature systems to name binary molecules:
1. Stock system for naming
New system– must understand oxidation numbers
Oxidation number: a number assigned to an atom in a molecular compound or molecular ion that indicates the general distribution of electrons among the bonded atoms (7-2)
2. Prefix system
Old system – based on numerical prefixes 1. mono hexa- 2. di- 7. hepta- 3. tri- 8. octa- 4. tetra- 9. nona- 5. penta deca-

17. Rules for Prefix System of Nomenclature of Binary Compounds:
1. Less-electronegative element is given first
First element only gets a prefix if it has more than one
Example: P4O10
2. Second element is named by combining
a) a prefix indicating the number of atoms
b) the root name of the second element
c) the ending -ide
Example: P4O10 = tetraphosphorous decoxide
3. The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel

18. The Binary Compounds of Nitrogen and Oxygen
Formula
Prefix-system name
N2O
Dinitrogen monoxide NO
Nitrogen monoxide
NO2
Nitrogen dioxide
N2O3
Dinitrogen trioxide
N2O4
Dinitrogen tetroxide
N2O5
Dinitrogen pentoxide
Illustration of how the prefix system is used

19. You Try! Name the following molecular compounds:
1. SO3
Sulfur trioxide
2. ICl3
Iodine trichloride
3. PBr5
Phosphorous pentabromide
Write formulas for the following molecular compounds:
1. Carbon tetraiodide
CI4
2. Phosphorous trichloride
PCl3
3. Oxygen difluoride
OF2

20. Practice Problems
Write the formula for the binary ionic compound formed between each of the following pairs of elements:
Give the names of the following compounds:
Potassium and sulfur
Ag2S
aluminum and chlorine
Ba(OH)2
cesium and sulfur
NH4NO3
Name the following binary ionic compounds:
Name the following binary molecular compounds:
BaF2
PF5
AgF
CCl4
K3N
N2O3
Write the formula and give the compound name formed between each of the following pairs of ions: (Stock system of nomenclature)
Write the formulas for the following compounds:
Carbon dioxide
Dinitrogen pentoxide
Cu+ and O2-
Sulfur hexafluoride
Fe3+ and S2-
Cu2+ and Cl-
(shortened version from original set for time purposes)