1. Cpt 7 Chemical formulas

2. Guided Reading, pages 164-170 What is a chemical symbol?
Why do they use them?
What is the format for a chemical symbol?
What do you call an atom that has become electrically charged?
There are two types of ions: cations and anions.
What is the difference between them?
Which type looses electrons?
Which type gains electrons?
What is formed when an anion bonds with a cation?
What is the difference between monatomic and polyatomic ions. Give examples.
What is the difference between chemical formulas and structural formulas? Give examples.
What is a diatomic molecule? List the 7 diatomic gases.
Define oxidation number.
What is the difference between ionic compounds and molecules? Explain in detail with examples.

3. Positive Ions (Cations)
Names, Formulas and Charges of Common Ions
Oxidation numbers of Common Monatomic and Polyatomic Ions – cations (positive ions)
Positive Ions (Cations) 1+ 2+ 3+ 4+
Ammonium
NH4+
Barium
Ba2+
Aluminum
Al3+
Tin(IV)
Sn4+
Cesium
Cs+
Calcium
Ca2+
Antimony(III)
Sb3+
(Stannic)
Copper(I)
Cu+
Chromium
Cr2+
Arsenic(III)
As3+
Lead(IV)
Pb4+
(Cuprous)
Cobalt
Co2+
Bismuth(III)
Bi3+
(Plumbic)
Francium
Fr+
Copper(II)
Cu2+
Boron
B3+
Manganese(IV)
Mn4+
Gold
Au+
(Cupric)
Chromium(III)
Cr3+
Hydrogen H+
Iron(II)
Fe2+
Cobalt(III)
Co3+
Lithium
Li+
(Ferrous)
Iron(III)
Fe3+
Potassium K+
Lead(II)
Pb2+
(Ferric)
Rubidium
Rb+
(Plumbus)
Titanium(III)
Ti3+
Silver
Ag+
Magnesium
Mg2+
Manganese(II)
Mn2+
Mercury(I)
Hg22+ 5+
(Mercurous)
Antimony(V)
Sb5+
Mercury(II)
Hg2+
Arsenic(V)
As5+
(Mercuric)
Bismuth(V)
Bi5+
Nickel(II)
Ni2+
Tin(II)
Sn2+
(Stannous)
Zinc
Zn2+

4. Negative Ions (Anions) Rules for Writing Chemical Formulae
Oxidation numbers of Common Monatomic and Polyatomic Ions – Anions (a negative ion)
Negative Ions (Anions) 1- 2- 3- 4-
Acetate
C2H3O2-
Carbonate
CO32-
Arsenate
AsO43-
Ferrocyanide
Fe(CN)64-
Bromate
BrO3-
Chromate
CrO42-
Borate
BO33-
(Hexacyanoferrate(II))
Bromide
Br-
Dichromate
Cr2O72-
Nitride
N3-
Silicate
SiO44-
Chlorate
ClO3-
Hydrogen-phosphate
HPO42-
Phosphate
PO43-
Chloride
Cl-
(Biphosphate)
Phosphite
PO33-
Cyanide
ClO2-
Oxalate
C2O42-
Phosphide
P43-
Dihydrogen
Oxide
O2-
phosphate
H2PO4-
Peroxide
O22-
Fluoride F-
Sulfate
SO42-
Rules for Writing Chemical Formulae
Hydride H-
Sulfide
S2-
RULE 1: The resulting formula for a compound must have a total net charge of zero (0).
RULE 2: Write the positive ion first and cross the valences.
RULE 3: Do not cross any signs, and don’t write any signs in the formula.
RULE 4: Don’t cross any ones.
RULE 5: If both valences are the same, don’t cross them.
RULE 6: More than one atom, more than one time, use parentheses.
RULE 7: If the final answer has subscripts that can be reduced, they must be reduced.
Bicarbonate
HCO3-
Sulfite
SO32-
Hydrogen
Thiosulfate
S2O32-
oxalate
HC2O4-
sulfate
HSO4-
sulfide
HS-
Some Common Acids
sulfite
HSO3-
Acetic
HC2H3O2
Hydroxide
Carbonic
H2CO3
Hypochlorite
ClO-
Hydrochloric
HCl
Iodide I-
Hydrobromic
HBr
Nitrate
NO3-
Hydrofluoric HF
Nitrite
NO2-
Nitric
HNO3
Perchlorate
ClO4-
Phosphoric
H3PO4
Permanganate
MnO4-
Sulfuric
H2SO4
Thiocyanate
SCN-

5. Formulas and Names of Binary Metal-Nonmetal Compounds
The name of the metal is first (ie: NaCl, sodium chloride)
The name of the nonmetal has -ide added (ie: NaCl sodium chloride)
IF the metal has more than one possible charge
You must indicate which ion using the charge in roman numerals (ie: FeCl2 Iron (II) chloride).
More examples showing the two different systems:
Compound
Name
FeF2
iron (II) fluoride
FeF3
iron (III)fluoride
Hg2Br2
mercury (I) bromide
HgBr2
mercury (II) bromide

6. Formulas and Names of Binary Nonmetal-Nonmetal Compounds
Systematic Nomenclature:
For names start with element to the left side on the periodic table
add -ide to the second element
use Greek prefixes for number of atoms: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca
Example:
CO carbon monoxide
CO2 carbon dioxide
N2O5 dinitrogen pentoxide
Formula
Systematic Name NO
nitrogen monoxide
N2O
dinitrogen monoxide
NO2
nitrogen dioxide
N2O5
dinitrogen pentoxide
N2O3
dinitrogen trioxide

7. Polyatomic Compounds. Naming compounds with polyatomic ions
Positive charge species on left (using common name)
Negative charge species on right (using name of polyatomic ion)
In the formula: use parentheses if a subscript is needed
Formula
Ions
Name
BaSO4
Ba2+ and SO42-
barium sulfate
Ca(NO3)2
Ca+2 and NO31-
calcium nitrate
Ca(NO2)2
Ca+2 and NO21-
calcium nitrite
Fe(NO3)2
Fe2+ and NO31-
iron (II) nitrate

8. Acids
Have their own set of rules (we do them in Cpt 23).
For now know:
HCl Hydrochloric Acid
HNO3 Nitric Acid
H2SO4 Sulfuric Acid

9. Naming Organic Compounds
carbon compounds that exist as molecules
We will focus on Hydrocarbons - Simplest group of organic compounds made of only H and C.
Carbon atoms can link in chains,branches, or rings.
Eg:

10. Rules for naming Hydrocarbons:
Count carbon atoms shown and find the prefix for it.
1 C = meth 6 = hex
2 = eth 7 = hept
3 = prop 8 = oct
4 = but 9 = non
5 = pent 10 = dec
Add a suffix to show how the carbon atoms link to each other. For now we only use –ane.

11. Methane: CH H
H C H H
Ethane C2H6
- C – C –
# H = #C x 2 + 2

12. More examples C C is cyclobutane If it’s a cycloalkane: #H = #C x 2
Do Page 178 # 13 and 14.

13. Molecular and Empirical Formulas
Molecular Formulas- used for compounds that exist as molecules;
Used for carbon compounds, 2 nonmetals together, or a nonmetal with Hydrogen
shows the actual number of atoms of each element making up a molecule. (Often the subscripts are not in lowest terms).
E.g. H20 and H2O2 and NO2 and C2H6 and CH4

14. Molecular and Empirical Formulas, continued
Empirical Formulas – used to show most ionic compounds.
Formula is given in the simplest ratio between the atoms present in the compound (this means subscripts are in lowest terms)
e.g. Al2(SO4) BaCl2

15. What is the empirical formula for C2H8?
A chemical formula is also called a formula unit.
Coefficients – used to show the number of formula units that you want to represent
3 H2O means you want 3 formula units of water.
Do page 180 #15-16