determining formulas the criss-cross method examples na +1 + o -2 ca +2 + p -3 c +4 + o -2 1...

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

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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.

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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” !

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Naming Compounds

Try these!

1. NaCl 2. Li3N

3. MgI2

Sodium Chloride

Lithium Nitride

Magnesium Iodide

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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

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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

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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

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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.

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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

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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

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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