You will learn: to write and read 4 types of chemical formulas
1. Ionic Compounds
2. Polyatomic Compounds
3. Molecular Covalent Compounds
4. Acids/ Bases
When 2 or more elements are chemically combined they are called a molecule or compound.
H2 + O2 H2O
Na + Cl NaCl
atom is the smallest whole unit of an element…….
A molecule is the smallest whole unit of a compound……..
Writing Chemical Formulas
Regardless of where or how a pure chemical compound is prepared, it is composed of a fixed proportion of elements.
“If it is water
it is always 2 hydrogen for every one oxygen… H2O
If it is carbon dioxide
it is always one carbon for every 2 oxygen…CO2…
**Law of Definite Proportions** **Law of Definite Proportions**
• Remember:– Valence Outer shell electrons involved in chemical reactions
– Octet Rule: Most stable condition is 8 electrons in outer shell
– Oxidation #: a + or – number which tells how many electrons were lost
gained
shared when bonding atoms.
Label empty periodic chartLabel empty periodic chart
Writing Ionic Binary Compounds(metal + nonmetal) ws 7.1
1. Write + oxidation number atom first 2. Write – oxidation number atom second3. Do cross-over method for subscripts4. The compound is in a neutral or “ground state”. The formula’s oxidation #’s must add up to equal zero. 5. Must have lowest common factor
Na + N Ca + P
Ba + F Mg + O
Ba + Sb Li + S
Ca + O Sc + Al
1. Write first element name2. Drop last syllable of second element and add ide 3. Transition metals use Roman Numerals to show
oxidation #
• LiF CuCl
NaBr CuCl2
KI FeO
Naming Binary Ionic Compounds
(Stock System) ws 7.2
Ternary Compounds
Polyatomic Ions Poly = many atoms in a group
When writing these formulas use the group as a whole.
Ca + ClO3
Na + SO4
NH4 + PO4
No need to use ( ) if only one group worksheet 7.3, 7.4
1. Nonmetals only 2. Prefixes give the number of each element
( show numbers)3. Second element ends in ide4. O or A at end of prefix is dropped if element
begins with a vowel. { monoxide … not---monooxide}{pentoxide … not– pentaoxide}
P4S5 tetraphosphorus pentasulfide
Si2Br6 disilicon hexabromide
CH4 carbon tetrahydride ws-7.7
Naming Molcular Compounds
Writing Formulas for Molecular Covalent Compounds NM + NM
• Follow wording… do NOT figure oxidation #
Antimony tribromide
Hexaboron monosilicide
Chlorine dioxidews 7.8
formulas for Molecular Covalent = NM+Nm
1. Make sure Nonmetals + Nonmetals
2. The less electronegative element is written first
3. The element written second will keep its normal negative oxidation #.
4. The first element will keep its normal oxidation # but will be positive.
5. Use the cross-over method
6. The algebraic sum of the ox# must equal zero
1. make sure NM + NM 2. The less electronegative element is written first3. The element written second will keep its normal negative oxidation #. 4. The first element will keep its normal oxidation # but will be positive. 5. Use the cross-over method6. The algebraic sum of the ox# must equal zero
Nitrogen + fluorine
Oxygen + sulfur
Phosphrous + chlorine
Bromine + carbon
Naming Acids 2 common types of Acids
Binary Acids OxyacidsHydrogen + one other element hydrogen + Polyatomic
w/Oxygen Hydro + root name & ic Root name + Suffix + acid
HBr hydrobromic acid If polyatomic ended in ‘ate’
HCl hydrochloric acid (NO3)- nitrate ion then
H2S hydrosulfuric acid HNO3 = nitric acid
HCN hydrocyanic acid (SO4)-2 sulfate ion then
H2SO4 = sulfuric acid
“notice hydrogen not part of name”
It is important to remember that these hydrogen – containing compounds are named as acids only when they are in water solutions.
Example: HCl----hydrogen chloride is a gas. But dissolved in water it is hydrochloric acid.
Memorize: HCl hydrochloric acid HNO3 nitric acid H2SO4 sulfuric acid
HC2H3O2 acetic acidH2CO3 carbonic acid H3PO4 phosphoric acid
We will learn more acids and bases in chapter 17 later I would put these on an index card
Acids and Bases
Six Acids to memorize
Hydrochloric
Nitric
Sulfuric
Phosphoric
Carbonic
Acetic
Bases:
metal + hydroxide
Sodium hydroxide
Potassium hydroxide
Calcium hydroxide
4 ways to name chemicals1st step----make sure you know
which method
M+NM NM+NM Ternary Compounds Acids
Nameing Oxyanions