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 1

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 or negative charge resulting from the loss or gain of one or more valence electrons. 2

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, Ca 2+ is calcium ion, Al 3+ is aluminum ion. 3

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 - ) 4

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. Fe 2+ is iron(II) ion Fe 3+ is iron(III) ion. 2. Classical – name of the element is used to form the root name for the element. Fe 2+ is ferr ous ion Fe 3+ is ferr ic ion 5

Symbols and Names of common Metal Ions Cu + Copper (I) ion Cuprous ion Cu 2+ Copper (II) ion Cupric ion Cd 2+ Cadmium ion Hg + Mercury (I) ion Mercurous ion Zn 2+ Zinc ion Hg 2+ Mercury (II) ion Mercuric ion Ag + Silver 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 6

Polyatomic Ions Polyatomic Ions are composed of more than one atom. 2- ) is composed of one sulfur atom and Sulfate ions (SO 4 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 . 7

Common Polyatomic Ions Charge 1 + NH 4 + Ammonium Charge 1 ─ C l O ¯ OH ¯ Hypochlorite Hydroxide ¯ CH 3 COO ¯ C l O 2 Chlorite Acetate ¯ CN ¯ C l O 3 Chlorate Cyanide ¯ OCN ¯ C l O 4 Perchlorate Cyanate ¯ ¯ lO 2 Iodite HSO 3 Bisulfite ¯ ¯ lO 3 Iodate HSO 4 Bisulfate ¯ ¯ lO 4 Periodate HCO 3 Bicarbonate ¯ ¯ NO 2 Nitrite BrO 3 Bromate ¯ ¯ NO 3 Nitrate MnO 4 Permanganate 8

Common Polyatomic Ions Charge 2 ─ 2− 2− CO 3 Carbonate CrO 4 Chromate 2− 2− O 2 Peroxide Cr 2 O 7 Dichromate 2− 2− SO 4 Sulfate C 2 O 4 Oxalate 2− 2− SO 3 Sulfite SiO 3 Silicate 2− S 2 O 3 Thiosulfate Charge 3 ─ 3− 3− PO 3 Phosphite AsO 3 Arsenite 3− 3− PO 4 Phosphate AsO 4 Arsenate 3− BO 3 Borate Charge 4 ─ 4− P 2 O 7 Pyrophosphate 9

Section 9.2 Naming Ionic Compounds 10

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. Cs 2 O is cesium oxide NaBr is sodium bromide Cu 2 O is copper(I) oxide CuO is copper(II) oxide 11

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 of the formula is zero. K + + Cl -  KCl Ca 2+ + Br -  CaBr 2 Fe 3+ + O 2-  Fe 2 O 3 Use the crisscross method – the numerical value of the charge of each ion is crossed over and becomes the 12 subscript for the other ion.

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. -  Ca(NO 3 ) 2 Ca 2+ + NO 3 2-  SrSO 3 Sr 2+ + SO 3 2-  Li 2 CO 3 Li + + CO 3 Use the crisscross method – the numerical value of the charge of each ion is crossed over and becomes the 13 subscript for the other ion.

Naming Polyatomic Ionic Compounds First recognize that the compound contains a polyatomic ion. State the cation first and then the anion NaC l O sodium hypochlorite (NH 4 ) 2 C 2 O 4 ammonium oxalate Li 2 CO 3 lithium carbonate 14

Section 9.3 Naming and Writing Formulas for Molecular Compounds 15

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, CO 2 ) Prefixes in the names of binary molecular compounds help distinguish compounds containing different amounts of the same two elements. 16

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 octa- 8 nona- 9 17 deca- 10

Naming Molecular Compounds The names of all binary molecular compounds end in – ide. CO is carbon monoxide CO 2 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. N 2 O is dinitrogen monoxide SF 6 is sulfur hexafluoride. 18

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 N 2 O 4 Diphosphorus trioxide P 2 O 3 19

Section 9.4 Naming and Writing Formulas for Acids and Bases 20

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 H n X. X is a monatomic or polyatomic anion n is a subscript indication the number of hydrogen ions combined with the anion. 21

Naming Acids Three rules are used to name acids. The name depends on 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. + Cl -  H + HCl Hydrogen ion chlor ide ion hydro chlor ic acid  H + + S 2- H 2 S Hydrogen ion sulf ide ion hydro sulfur ic acid 22

Naming Acids Three rules are used to name acids. The name depends on 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 + 2- + SO 3 H 2 SO 3 Hydrogen ion sulf ite ion sulfur ous acid  H + - + CIO 2 HCIO 2 Hydrogen ion chlor ite ion chlor ous acid 23

Naming Acids Three rules are used to name acids. The name depends on 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 + - + NO 3 HNO 3 Hydrogen ion nitr ate ion nitr ic acid  H + 2- + SO 4 H 2 SO 4 Hydrogen ion sulf ate ion sulfur ic acid 24

Writing Formulas for Acids Use the rules for writing the names of acids in reverse to write the formula for acids. Hydro brom ic acid H ydro indicates the brom ide ion HBr Phosphor ous acid - ous indicates the phosph ite ion H 3 PO 3 phosphor ic acid -ic and beginning with the anion name indicates the phosph ate ion H 3 PO 4 25