1. Chapter 7 – Chemical Formulas and Chemical Compounds
Pereira- Honors Chemistry Class

2. 7-1 Chemical Names and Formulas
What’s so important about a chemical formula?
It indicates the relative # of atoms of each kind in a chemical compound
Molecular Compound: chemical formula reveals the # of atoms in a single molecule. C8H18
Ionic Compound: consists of a lattice of positive and negative ions held together by mutual attraction.  Simplest ratio NaCl

3. Al2(SO4)3- How many atoms are there?12

4. Monoatomic Ions Ions formed from a single atom Ex. Na  Na1+ , O  O2-
Not all main-group elements form ions, C and Si form covalent bonds instead of ionic bonds
Sn and Pb are exceptions  lose only 2 e-s instead of 4 or sometimes they keep all 4 electrons.

5. Naming Monoatomic Ions
Cations are identified by the elements name
Anions the ending of the element’s name is dropped.
The ending –ide is added.
Ex. Fluorine (F) = Fluoride ion (F-)
Nitrogen (N) = Nitride (N3-)
Flash Cards may be useful to memorize these!!!!

6. Binary Ionic Compounds
Compounds composed of two different elements.
Ex. Magnesium and Bromine form Magnesium Bromide, MgBr2

7. Rules for Ionic Compounds
1. Write the symbols for the ions side by side. The cations go first.
Al 3+ O 2-
2. Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other ion.
Al2O3
3. Check subscript and divide them by their largest common factor to give the smallest possible whole-number ration.
4. Write the formula

8. Write the formula for the following:
Magnesium and iodine
Potassium and sulfur
Aluminum and chlorine
Zinc and bromine
Cesium and sulfur
Strontium and oxygen
Calcium and nitrogen
MgI2
K2S
AlCl3
ZnBr2
Cs2S
SrO
Ca3N2

9. Name the following: BaF2 CaO AgF CdO K3N NaI AlBr3 Barium Fluoride
Calcium Oxide
Silver Fluoride
Cadmium Oxide
Potassium Nitride
Sodium Iodide
Aluminum Bromide

10. The Stock System of Nomenclature
Some elements form two or more ions such as Fe, with different charges.
This system uses Roman numerals to indicate an ions’ charge
Fe 2+ or Fe 3+
FeCl2 = iron (II) chloride
FeCl3 = iron (III) chloride

11. Write the formula and give the name for the following:
Cu + and O 2-
Fe 3+ and S 2-
Cu 2+ and Cl -
Sn 2+ and Cl -
Hg 2+ and O 2-
Sn4+ and S 2-
V 2+ and F -
V 4+ and Br -

12. Name the following:
CoI2
HgI2
PbS2
CuBr2

13. Compounds Containing Polyatomic ions
Oxyanions- polyatomic ions containing oxygen
Nitrate vs. Nitrite – (-ite less oxygen)
NO3- and NO2-
Sulfates, Nitrate, Chlorates

14. Write the formulas for:
Copper(II) nitrate
Potassium iodide
Sodium hydroxide
Ammonium acetate
Calcium carbonate
Potassium permanganate
Sodium sulfate
Iron(III) nitrate

15. Name the following: Ag2S NaMnO4 Ba(OH)2 NH4NO3 Fe(ClO)2 Ca(NO3)2 K2SO3
NaCH3COO

16. Naming Binary Molecular Compounds# 1 2 3 4 5 6 7 8 9 10 #
Mono Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
deca

17. Rules for Molecular Compounds
1. The least electronegative element is first. It is given a prefix if it is more than one
2. the second element is named by combining a prefix, the root of the word, and –ide ending
3. the o or a at the end of the prfix is usually dropped when the word following begins with another vowel.

18. Examples. As2O5 = diarsenic pentoxide PF5 = phosphorus pentafluoride
XeF4 = Xenon tetrafluoride
CCl4 = carbon tetrachloride
Carbon dioxide = CO2
Dinitrogen pentoxide = N2O5
Sulfur hexafluoride = SF6
Dinitrogen monoxide = N2O

19. Acids and Salts Acids can be binary acids or oxyacids
Binary acids are acids that consist of H and a halogen, HCl hydrochloric acid
Oxyacids, contain H, P and a third element, Sulfuric Acid, H2S
Pg 214