Nomenclature and Formulas of Ionic Compounds. Section I: Writing the Name from the Formula

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Purpose: 1. To become familiar with the rules of chemical nomenclature, based on the classification of compounds.

2. To write the proper name of the compound when given the formula. 3. To write the proper formula when given the name.

Theory: • Metals form positive ions (cations) and non-metals form negative ions (anions).

• Chemical Formulas of ionic compounds result from combining cations with anions in ratios that result in a net charge of zero for the compound.

• Chemical Nomenclature depends on the types of cations and anions present. Cations and anions take different forms:

• Representative Metal Cations always take the same positive charge. (Groups 1a, 2a, Al+3, Zn+2, Cd+2) • Transition Metal Cations can vary in charge, but are always positive. ( Examples: Fe2+ and Fe3+ ) • Polyatomic cations contain groups of atoms acting as a single positive ion. ( Most common is NH4+1)

• Representative Nonmetal Anions always take the same negative charge. (Groups 5a, 6a, 7a) • Polyatomic anions contain groups of atoms acting as a single negative ion. (The list is extensive)

Names of ionic compounds depends on recognizing the type of cation and anion present. Each type employs a different set of rules for writing names. It is absolutely importanct to get the right classification, since using the wrong set of rules will result in an improper name.

There are several approaches to Nomenclature. The following is a summary of the common sets of rules found in most textbooks.

NOTE: For best results, keep a periodic table handy.

Section I: Writing the Name from the Formula

If the formula contains: The compound is: Go to:

One metal element

and Binary Part 1--Binary Compounds

One nonmetal element

More than two elements Polyatomic Part 2--Polyatomic Ions

Hydrogen as the first An Acid Part 3--Acids

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Section I: Writing the Name from the Formula

Part 1. Binary Ionic Compounds ----> Is the metal is representative or transition? a. Representative Metal Cation + Representative Nonmetal Anion.

• Includes: Metals: Groups 1a, 2a, Al (also Ag, Zn, Cd)

Nonmetals: Groups 7a, 6a, (and sometimes 5a) 1a 2a 3a 4a 5a 6a 7a Li Be N O F Na Mg Al P S Cl K Ca Zn Br Rb Sr Ag Cd I Cs Ba Fr Ra

Rule: State the name of the metal, change the nonmetal ending to -ide.

NaCl _CdBr2 SrS _Al2O3

Sodium chloride Cadmium Bromide Strontium sulfide Aluminum oxide

b. Transition Metal Cation + Representative Nonmetal Anion

• Includes: Metals: Most d-block transition metals, Sn, Pb, U Nonmetals: Groups 7a, 6a, and sometimes 5a

1a 2a 3a 4a 5a 6a 7a N O F P S Cl Sc Ti V Cr Mn Fe Co Ni Cu Br Sn I Pt Au Hg Pb

Rule: • State the name of the metal

• Determine the charge of the cation, based on known charge of the anion. • Write the charge in Roman Numerals placed in brackets.

• Change the nonmetal ending to -ide.

CuBr _Fe2O3 _HgCl2 _PbS2

Cu+1 Br-1 Fe+3 O-2 Hg+2 Cl-1 Pb+4 S-2

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Part 2. Polyatomic Ions ----> Ionic compounds containing more than two elements.

Table of Common Polyatomic Ions

Ammonium ion _{NH4 +1} (This is the only common polyatomic cation.) Acetate ion _{C2H3O2 -1} _{(Sometimes written CH3COO -1)}

Bicarbonate ion _{HCO3 -1} (aka Hydrogen Carbonate ion) Carbonate ion _{CO3 -2}

Nitrate ion _{NO3 -1} Nitrite ion _{NO2 -1}

Phosphite ion _{PO3 -3} Phosphate ion _{PO4 -3} Monohydrogen Phosphate _{HPO4 -2} Dihydrogen Phosphate _{H2PO4 -1}

Sulfite ion _{SO3 -2} Sulfate ion _{SO4 -2}

Hypochlorite ion ClO -1 Cyanide ion CN -1

Chlorite ion _{ClO2 -1} Hydroxide ion OH-1

Chlorate ion _{ClO3 -1} Peroxide ion _{O2 - 2}

Perchlorate ion _{ClO4 -1} Permanganate ion _MnO4-1

a. Representative Metal Cation + Polyatomic Anion

Rule: State the name of the metal, then the name of the polyatomic ion.

Na2SO4 Ca(CN)2 LiC2H3O2 Zn3(PO4)2

Sodium sulfate Calcium cyanide Lithium acetate Zinc phosphate

b. Transition Metal Cation + Polyatomic Ion

Rule: State the name of the metal, with the Roman Numeral charge in brackets, followed by the name of the polyatomic ion.

Sn(OH)2 Co (NO3)6 Ni (C2H3O2)5 AuPO4

Sn+2 (OH)-1 _{Co+6 (NO3)-1} _{Ni+5 (C2H3O2)-1} _{Au+3 (PO4)-3} Tin [II] hydroxide Cobalt [VI] nitrate Nickel [V] acetate Gold[III] phosphate

c. Ammonium ion ( NH4+1 )

Rule: Start the name with “Ammonium”, followed by the name of the anion. NH4 Cl (NH4) 2O NH4C2H3O2 (NH4) 3PO4 Ammonium chloride Ammonium oxide Ammonium acetate Ammonium phosphate

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Section I: Writing the Name from the Formula

Part 3. Acids--Contain hydrogen as the positive ion.

A. Binary Acids -- contain hydrogen plus one nonmetal element. (NO oxygens)

Rule: a. Begin the name with “hydro-”. b. Change the ending to “-ic.”

c. Add the word “acid” to the end.

HF HCl HBr HI _H2S

Hydrofluoric Hydrochloric Hydrobromic Hydroiodic Hydrosulfuric

Acid Acid Acid Acid Acid

B. Ternary Acids (Oxy-Acids) -- Formula begins with hydrogen, and contains oxygen.

Rule: a. Identify the polyatomic ion, and change the ending as follows:

Formula Name Acid nomenclature

C2H3O2 -1 Acetate Acetic

SO3 -2 Sulfite Sulfurous

SO4 -2 Sulfate Sulfuric

NO2 -1 Nitrite Nitrous

NO3 -1 Nitrate Nitric

PO3 -3 Phosphite Phosphorous

PO4 -3 Phosphate Phosphoric

ClO -1 Hypochlorite Hypochlorous

ClO2 -1 Chlorite Chlorous

ClO3 -1 Chlorate Chloric

ClO4 -1 Perchlorate Perchloric

b. Add the word “acid” to the end.

H2SO4 H2SO3 HNO3 H3PO4

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Metal is: And ends in: The compound is: Go to:

Representative “-ide” Binary Part 1

(Groups 1a, 2a,

or Ag, Cd, Zn) NOT “-ide” Polyatomic Part 3

Roman Numeral “-ide” Transition metal Part 2

(Most transition metals)

NOT “ide” Polyatomic Part 3

Acids Part 4

Part 1 -- Formulas of Binary Ionic Compounds with Representative Elements

• Includes:

Metals: Nonmetals:

Group 1a ( Li+1, Na+1, K+1, Rb+1, Cs+1, Fr+1) Group 7a ( F-1, Cl-1, Br-1, I-1 )

Group, 2a (Be+2, Mg+2, Ca+2, Sr+2, Ba+2, Ra+2 ) Group 6a ( O-2, S-2)

Group 3a (Al+3 only) Group 5a (N-3, P-3 )

Also ( Ag+1, Zn+2, Cd+2 )

• How to Proceed: Magnesium Oxide

a. Write the Symbols of both elements... Mg O

(Metal first, followed by the nonmetal )

b. Determine the charge of the ions from ... Mg+2 O-2

their positions on the Periodic Table.

c. “Cross multiply” to balance the charges... _{Mg +2 O -2}

2 2

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Section 2, Writing the Formula From the Name

Part 2 --Formulas of Binary Ionic Compounds with Transition Metals •Includes: Most d-block metals; Sn, and Pb.

(For d-block, exceptions, see part 1, above.)

• How to Proceed: Manganese (IV) Oxide

a. Write the Symbols of both elements... Mn O

b. Determine the charge of the transition... Mn 4+

metal ion from the Roman Numeral.

Use the Periodic Table to determine... O -2

the charge of the Nonmetal.

c. “Cross multiply to balance the charges... _{Mn 4+ O -2}

₂ ₄

d. Reduce the formula, if necessary... Mn2O4 MnO2

Part 3--Polyatomic Ions :

• Includes: At least one polyatomic ion

Consult the list of common polyatomic ionsgiven above, or in other texts.

• How to Proceed Cobalt [VI] Phosphate

a. Write the symbols for the ions. ... Co PO4 -3 b. Determine the charge of the metal... Co+6

ion using the rules from Pts. 1&2

c. “Cross multiply” to balance the charges... Co+6 PO4-3

3 6

d. Use parentheses to enclose

the polyatomic ion if needed... _{Co3 (PO4)6} e. Reduce, if necessary... _Co(PO4)2

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Part 4. Acids

A. Binary Acids -- Contain the prefix “hydro-” . Hydrofluoric acid

• How to Proceed:

a. The name gives the component elements... (H+1) (F-1)

b. Balance the charges as with ionic compounds... HF

B. Ternary Acids (Oxy-acids) -- Do NOT contain the prefix “hydro-”.

• How to Proceed

a. Match the ending with the proper polyatomic ion. (Use the Table in Section 1 above)

Nomenclature and Formulas of Ionic Compounds. Section I: Writing the Name from the Formula

Section I: Writing the Name from the Formula

Sulfuric Acid

Sulfurous Acid

Sulfate Ion (SO4-2)

_{Sulfite Ion (SO3-2)}