Chapter 9 Chemical Names and Formulas Section 9.1 Naming Ions 1 - - PowerPoint PPT Presentation

Chapter 9 Chemical Names and Formulas Section 9.1 Naming Ions

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Monatomic Ions

Ionic compounds consist of a positive metal ion and a negative nonmetal ion combined in a proportion such that their charges add up to a net charge of zero. NaCl – consists of one Na+ and one Cl-. Monatomic ions consists of a single atom with a positive

• r negative charge resulting from the loss or gain of one
• r more valence electrons.

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Monatomic Ions - Cations

Cations tend to lose valence electrons. (1+ charge – lose 1 electron, 2+ charge – lose 2 electrons, etc. ) When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number. The name of the cations of the Group 1A, 2A and 3A are the same as the name of the metal, followed by the word ion or cation. Na+ is sodium ion, Ca2+ is calcium ion, Al3+ is aluminum ion.

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Monatomic Ions - Anions

Nonmetals tend to gain electrons to form anions, so the charge of a nonmetallic ion is negative. The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number. Group 7A form anions with a 1- charge (7-8 = -1) Anion names start with the stem of the element name and end in –ide. Anion of fluorine is fluoride ion (F-), anion of chlorine is chloride ion (Cl-)

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Ions of Transition Metals

Many of the transition metals (Group 1B – 8B) form more than one cation with different ionic charges. Two methods are used to name these ions.

• 1. Stock System – a roman numeral in parentheses is

placed after the name of the element to indicate the numerical value of the charge. Fe2+ is iron(II) ion Fe3+ is iron(III) ion.

• 2. Classical – name of the element is used to form the

root name for the element. Fe2+ is ferrous ion Fe3+ is ferric ion

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Symbols and Names of common Metal Ions Cu + Copper (I) ion Cuprous ion Cu 2+ Copper (II) ion Cupric ion Hg + Mercury (I) ion Mercurous ion Hg 2+ Mercury (II) ion Mercuric ion Fe 2+ Iron (II) ion Ferrous ion Fe 3+ Iron (III) ion Ferric ion Cr 2+ Chromium (II) ion Chromous ion Cr 3+ Chromium (III) ion Chromic ion Mn 2+ Manganese (II) ion Manganous ion Mn 3+ Manganese (III) ion Manganic ion Co 2+ Cobalt (II) ion Cobaltous ion Co 3+ Cobalt (III) ion Cobaltic ion Pb 2+ Lead (II) ion Plumbous ion Pb 4+ Lead (IV) ion Plumbic ion Sn 2+ Tin (II) ion Stannous ion Sn 4+ Tin (IV) ion Stannic ion Cd 2+ Cadmium ion Zn 2+ Zinc ion Ag + Silver ion

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Polyatomic Ions

Polyatomic Ions are composed of more than one atom. Sulfate ions (SO4

2-) is composed of one sulfur atom and

four oxygen atoms. Polyatomic ions are a tightly bound group of atoms that behave as a unit and carry a charge. The names of most polyatomic anions end in –ite or –ate.

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Common Polyatomic Ions Charge 1 + NH4 + Ammonium Charge 1 ─ ClO ¯ Hypochlorite OH ¯ Hydroxide ClO2

¯

Chlorite CH3COO ¯ Acetate ClO3

¯

Chlorate CN ¯ Cyanide ClO4

¯

Perchlorate OCN ¯ Cyanate lO2

¯

Iodite HSO3

¯

Bisulfite lO3

¯

Iodate HSO4

¯

Bisulfate lO4

¯

Periodate HCO3

¯

Bicarbonate NO2

¯

Nitrite BrO3

¯

Bromate NO3

¯

Nitrate MnO4

¯

Permanganate

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Common Polyatomic Ions Charge 2 ─ CO3

2−

Carbonate CrO4

2−

Chromate O2

2−

Peroxide Cr2O7

2−

Dichromate SO4

2−

Sulfate C2O4

2−

Oxalate SO3

2−

Sulfite SiO3

2−

Silicate S2O3

2−

Thiosulfate Charge 3 ─ PO3

3−

Phosphite AsO3

3−

Arsenite PO4

3−

Phosphate AsO4

3−

Arsenate BO3

3−

Borate Charge 4 ─ P2O7

4−

Pyrophosphate

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Section 9.2 Naming Ionic Compounds

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Naming Binary Ionic Compounds

A binary compound is composed of two elements and can be either ionic or molecular (covalent). To name any binary ionic compound, place the cation name first, followed by the anion name. Cs2O is cesium oxide NaBr is sodium bromide Cu2O is copper(I) oxide CuO is copper(II) oxide

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Writing Formulas Binary Ionic Compounds

Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges. The positive charge of the cation must balance the negative charge of the anion so that the net ionic charge

• f the formula is zero.

K+ + Cl-  KCl Ca2+ + Br -  CaBr2 Fe3+ + O2-  Fe2O3 Use the crisscross method – the numerical value of the charge of each ion is crossed over and becomes the subscript for the other ion.

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Writing Formulas Polyatomic Ionic Compounds

An –ate or –ite ending on the name of a compound indicates that the compound contains a polyatomic anion that includes oxygen. Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges. Ca2+ + NO3

•  Ca(NO3)2

Sr2+ + SO3

2-  SrSO3

Li+ + CO3

2-  Li2CO3

Use the crisscross method – the numerical value of the charge of each ion is crossed over and becomes the subscript for the other ion.

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Naming Polyatomic Ionic Compounds

First recognize that the compound contains a polyatomic ion. State the cation first and then the anion NaClO sodium hypochlorite (NH4)2C2O4 ammonium oxalate Li2CO3 lithium carbonate

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Section 9.3 Naming and Writing Formulas for Molecular Compounds

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Naming Molecular Compounds

Binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal. Binary molecular compounds are composed of two elements, two nonmetals and they are not ions. Binary molecular compounds are composed of molecules, not ions, so ionic charges cannot be used to write formulas or to name them. In addition, when two nonmetallic elements combine, they often do so in more than one way. (CO, CO2) Prefixes in the names of binary molecular compounds help distinguish compounds containing different amounts of the same two elements.

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Naming Molecular Compounds

The prefix in the name of a binary molecular compound tells how many atoms of each element are present in each molecule of the compound.

Prefix Number mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7

• cta-

8 nona- 9 deca- 10

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Naming Molecular Compounds

The names of all binary molecular compounds end in –ide. CO is carbon monoxide CO2 is carbon dioxide If just one atom of the first element is in the formula, omit the prefix mono-

• Name the elements in order listed in the formula
• Use prefixed to indicate the number of each kind of atom
• The suffix of the name of the second element is –ide.

N2O is dinitrogen monoxide SF6 is sulfur hexafluoride.

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Writing Formulas Molecular Compounds

Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts.

Dinitrogen tetraoxide N2O4 Diphosphorus trioxide P2O3

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Section 9.4 Naming and Writing Formulas for Acids and Bases

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Naming Acids

Acid is a compound that contains one or more hydrogen atoms and produces hydrogen ions (H+) when dissolved in water. When naming acids, the acid consists of an anion combined with as many hydrogen ions as needed to make the molecule electrically neutral. The general chemical formulas of acids is HnX. X is a monatomic or polyatomic anion n is a subscript indication the number of hydrogen ions combined with the anion.

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Naming Acids

Three rules are used to name acids. The name depends

• n the name of the anion and its suffix (-ide, -ite, -ate)
• 1. a. When the name of the anion ends in –ide, the acid

name begins with the prefix hydro-.

• b. The stem of the anion has the suffix –ic and is

followed by the word acid. H+ + Cl -  HCl

Hydrogen ion chloride ion hydrochloric acid

H+ + S2-  H2S

Hydrogen ion sulfide ion hydrosulfuric acid

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Naming Acids

Three rules are used to name acids. The name depends

• n the name of the anion and its suffix (-ide, -ite, -ate)
• 2. a. When the anion name ends in –ite, the acid name

is the stem of the anion with the suffix –ous, followed by the word acid H+ + SO3

2-

 H2SO3

Hydrogen ion sulfite ion sulfurous acid

H+ + CIO2

• 

HCIO2

Hydrogen ion chlorite ion chlorous acid

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Naming Acids

Three rules are used to name acids. The name depends

• n the name of the anion and its suffix (-ide, -ite, -ate)
• 3. a. When the anion name end in –ate, the acid name

is the stem of the anion with the suffix –ic followed by the word acid. H+ + NO3

• 

HNO3

Hydrogen ion nitrate ion nitric acid

H+ + SO4

2-

 H2SO4

Hydrogen ion sulfate ion sulfuric acid

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Writing Formulas for Acids

Use the rules for writing the names of acids in reverse to write the formula for acids. Hydrobromic acid Hydro indicates the bromide ion HBr Phosphorous acid

• ous indicates the phosphite ion

H3PO3 phosphoric acid

• ic and beginning with the anion name indicates the phosphate ion

H3PO4

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Bases

A base is an ionic compound that produced hydroxide ions (OH-) when dissolved in water. Bases are named the same way as other ionic compounds – the name of the cation is followed by the name of the anion. NaOH is sodium hydroxide To write the formulas for bases, write the symbol for the cation followed by the formula for the hydroxide ion. (then use the crisscross method to write the formula as you do as you do for any ionic compound) Aluminum hydroxide – Al3+ + OH-  Al(OH)3 Ammonium hydroxide – NH4

+ + OH-  NH4OH

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