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Determining FormulasThe Criss-Cross Method
Examples
Na+1 + O-2
Ca+2 + P-3
C+4 + O-2 1
Na2O
Ca3P2
C2O4 reduced to CO2
2
Naming Compounds
Chemical Nomenclature--> system used to name chemical substances.
The Name of a compound indicates the composition of the substance.
From the name one can deduce a chemical formula.
3
Naming Binary Compounds
The first element is named as usual but only a stem of the second is used followed by the suffix “ide”
For example: MgCl2 is Magnesium chloride
: Al2O3 is Aluminum Oxide
The Chlorine and Oxygen must change their suffix from “ine” and “ygen” to “ide” !
4
Naming Compounds
Try these!
1. NaCl 2. Li3N
3. MgI2
Sodium Chloride
Lithium Nitride
Magnesium Iodide
5
Stock System for Transitional Metals
A compound that contains a transitional metal must be named so that the oxidation # of the metal is identified.
A Roman numeral is placed after the metal. It represents the oxidation # of the metal.
Ex. FeCl3 Iron (III) Chloride
CuCl2 Copper (II) Chloride
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Assigning Oxidation # Transitional Metals
The total charge on any compound or molecule is always equal to zero.
To determine unknown oxidation #s, add up the oxidation #s of the Cation and Anion and set them equal to zero. (Create an algebra formula and solve for X.)
Example Cr2O3 total charge = 0
Cr = x , O = -2Formula 2x + 3(-2)= 0 2x-6= 0 x= +3
Cr= +3
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Naming Transitional Metal Compound
Name These,
1) FeCl2
2) CrO2
3) NiP
Iron(II) ChlorideChromium(IV) Oxide
Nickel(III) Phosphide
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Common Names The old naming system Latin Names
Antimony Sb Stibium
Copper Cu Cuprum
Gold Au Aurum
Iron Fe Ferrum
Lead Pb Plumbum
Mercury Hg Hydragyrum
Potassium K Kalium
Silver Ag Argentum
Sodium Na Natrium
Tin Sn Stannum
Tungsten W Wolfram
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Naming Molecules(Using prefixes)
If two non-metals are bonded covalently, the name can be shown using prefixes.
The number of atoms for each element in a molecule is usually indicated by the
prefix:
– mono - 1 atom - hexa - 6 atoms
– di - 2 atoms - hepta - 7 atoms– tri - 3 atoms - octa - 8 atoms– tetra - 4 atoms– penta - 5 atoms
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Naming Molecules
Examples:
nitrogen dioxide is NO2
dinitrogen pentoxide is N2O5
phosphorus tribromide is PBr3
The prefix represents the subscript. If the subscript is one mono is not needed.
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Binary Molecules
Name these ::: Use Old Naming system and Stock system
1. PCl3
2. PCl5
3. SO2
Phosphorus TriChloride
Sulfer (IV) OxideSulfur Dioxide
Phosphorus(V) Chloride
Phosphorus(III) Chloride
Phosphorus PentaChloride
12
Poly-Compounds
Formulas of compounds containing polyatomic ions are written in a manner to stress the fact that the ions are independent units
An example is Sodium Nitrate which contains the nitrate ion (NO3)-1 is written NaNO3
13
POLY-ATOMIC IONSFormula Name
(NH4)+1 Ammonium
(C2H3O2)-1 Acetate
(ClO3)-1 Chlorate
(CN)-1 Cyanide
(OH)-1 Hydroxide
(HCO3)-1 Bicarbonate
(NO3)-1 Nitrate
(CO3)-2 Carbonate
(CrO4)-2 Chromate
(O2)-2 Peroxide
(SO4)-2 Sulfate
(PO4)-3 Phosphate
Poly-atomic Poly-atomic ionsions Two or more atoms covalently bonded but as a group carry a charge.
Pg 226 lists many more poly-
atomic ions Memorize ionsMemorize ions.all
12
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Poly-Compounds
When naming these compounds the name of the poly-ion is unchanged.
Examples 1. Na2SO4 Sodium Sulfate
2. (NH4)2Se Ammonium Selenide
If Ammonium is the poly-atomic ion, the non-metal still maintains its “ide” suffix.
15
Poly-Compounds
If a compound contains a polyatomic ion with a subscript of two or more the ion is enclosed in parenthesis:
Example: – calcium bicarbonate Ca(HCO3)2
– ammonium sulfide (NH4)2S
16
Poly-Compounds
Name these ::: Go to page 226 or your packet for help.
1. Ca(ClO3)2
2. NH4OH
3. Cr(SO4)2
Memorize the 12 Common Poly-atomic Ions.
There will be an Ion quiz very soon.
Calcium Chlorate
Ammonium Hydroxide
Chromium(IV) Sulfate
17
Oxy-IonsOxy-Ions
Polyatomic Ions containing Oxygen can be represented a number of different ways.
If one less Oxygen in the formula. The suffix is changed from “ate” to “ite”. The ion’s charge The ion’s charge does not change.does not change. Ex. (NO3)-1 Nitrate vs. (NO2)-1 Nitrite
If two less Oxygens the prefix “hypo-” is placed in front of the “ite” name.
Ex. (ClO)-1 hypohypo- Chlorite If one more Oxygen the prefix “per-” is placed in
front of the “ate” name. Ex. (ClO4)-1 PerPer Chlorate
Acids
Acids have their own naming system and they must be recognized when
dealing with nomenclature.
The name acid comes from the Latin term for “sour” {Acids are sour to the taste}
Acids are substances that donate protons (H+) {usually when dissolved in
water}
The Chemical formula almost always begins with Hydrogen
Example: hydrochloric acid HCl sulfuric acid H2SO4
Naming Acids
Lets separate acids into 2 types:
Acids that contain oxygen
H3PO4 H2SO4
HNO3 H2O
Acids that do not contain oxygen
HCl HBrHF H2S
Naming AcidsNaming acids containing oxygen:
For acids containing “-ate” anions:1. Use root of the anion (for sulfate, SO4
2-, use sulfur) 2. Add “-ic” suffix then end with “acid”
Example: H3PO4 is Phosphoric acid
For acids with “-ite” anions:1. Use root of the anion (for sulfite, SO3
2-, use sulfur) 2. Add “-ous” suffix then end with “acid”
Example: H2SO3 is sulfurous acid
Naming Acids (cont.)
Naming acids not containing oxygen:– Add “hydro-” prefix to beginning– Use root of the anion (i.e. Cl- use chlor)– Add “-ic” suffix then end with “acid”Example: HCl is hydrochloric acid
Name the following acids:HFHNO2
HCNH3PO4
Hydrate Molecules A hydrate molecule is a ionic
compound that contains water molecules trapped inside the crystalline structure.
The Formula includes a dot followed by the number of water molecules
Ex: Copper(II) Sulfate Pentahydrate
CuSO4 · 5H2O
Hydrate MoleculesThe Name of a hydrate molecule
would include two separate names.
To name, use the name of the ionic compound followed by the term … hydrate. A Greek Prefix would be used to represent the number of water molecules that are trapped.
CoCl2 · 2 H2O
Colbalt(II) Chloride Dihydrate