Objectives l PSc –Predict chemical formulas and names for simple compounds based on knowledge of bond formation and naming conventions.

Naming Compounds and Writing Formulas

Systematic Naming l There are too many compounds to remember the names of them all. l A compound is made of two or more elements. l The name should tell us how many and what type of atoms.

Types of Compounds l There are two types of compounds: ionic compounds and molecular (covalent) compounds.

Ionic Compounds l The simplest ratio of the ions represented in an ionic compound is called a formula unit. l The overall charge of any formula unit is zero. l In order to write a correct formula unit, one must know the charge of each ion.

Charges on Ions: Oxidation Numbers

Naming Cations l We will use the systematic way. l For cations, if the charge is always the same (Group A) just write the name of the metal.

Naming Cations l Tin and lead can have more than one type of charge. l Indicate the charge with Roman numerals in parenthesis.

Example l Li 1+  Li is the symbol for lithium.  Lithium is a Group 1A metal, so the charge is always the same. Write the name of the metal.  Li 1+ is called the Lithium ion.

Example l Sr 2+  Sr is the symbol for strontium.  Strontium is a Group 2A metal, so the charge is always the same. Write the name of the metal.  Sr 2+ is called the Strontium ion.

Example l Sn 2+  Sn is the symbol for tin.  Tin has multiple oxidation numbers. Write the name of the metal, indicating the charge with Roman numerals in parenthesis.  Sn 2+ is called the Tin (II) ion.

Example l Pb 4+  Pb is the symbol for lead.  Lead is a Group 4A metal, and the charge is not always the same. Write the name of the metal, indicating the charge with Roman numerals in parenthesis.  Pb 4+ is called the Lead (IV) ion.

Problem l Name the following cations.  Ca 2+  Sn 4+ Ca lcium ion  Al 3+ Alumin um ion Tin (IV) ion

Writing the Formulas for Cations l Write the formula for the metal. l If a Roman numeral is in parenthesis use that number for the charge. Indicate the charge with a superscript.

Writing the Formulas for Cations l If no Roman numeral is given, find the Group A metal on the periodic table and determine the charge from the column number.

Example l Lead (II) ion  Pb is the symbol for lead.  Lead has multiple charges, which is the reason why the charge with Roman numerals in parenthesis was included.  The formula for the lead (II) ion is Pb 2+.

Example l Gallium ion  Ga is the symbol for gallium.  Gallium is a Group 3A metal and its charge is always the same (3+).  The formula for the gallium ion is Ga 3+.

Problem l Write the formulas for the following cations.  Copper (II) ion  Magnesium ion  Potassium ion Mg 2+ Cu 2+ K 1+

Problem l Write the formulas for the following ions.  Chromium (VI) ion  Aluminum ion  Mercury (II) ion Al 3+ Cr 6+ Hg 2+

Naming Anions l Naming monatomic anions is always the same. l Change the element ending to – ide l Example: F 1- l F is the symbol for fluorine, F 1- is ide.fluorine.

Example l Cl 1-  Cl is the symbol for chlorine.  Chlorine is a Group 7A nonmetal, so the charge is always the same (1-).  Cl 1- is called the chloride ion.

Example l O 2-  O is the symbol for oxygen.  Oxygen is a Group 6A nonmetal, so the charge is always the same (2-).  O 2- is called the oxide ion.

Problem l Name the following anions.  S 2- sulfide ion  Br 1- bromide ion  N 3- nitride ion

Problem l Name the following anions.  As 3- arsenide ion  Te 2- telluride ion

Writing the Formulas for Anions l Write the formula for the nonmetal. l Find the Group A nonmetal on the periodic table and determine the charge from the column number.

Problem l Write the formulas for the following anions.  iodide ion I 1-  phosphide ion P 3-

Problem l Write the formulas for the following anions.  selenide ion Se 2-  carbide ion C 4-

Ionic Compounds l Oxidation numbers can be used to determine the chemical formulas for ionic compounds. l If the oxidation number of each ion is multiplied by the number of that ion present in a formula unit, and then the results are added, the sum must be zero.

Ionic Compounds l In the formula for an ionic compound, the symbol of the cation is written before that of the anion. l Subscripts, or small numbers written to the lower right of the chemical symbols, show the numbers of ions of each type present in a formula unit.

Binary Ionic Compounds l Binary ionic compounds are composed of a metal bonded with a nonmetal. l Name the metal ion using a Roman numeral in parenthesis if necessary. l Follow this name with the name of the nonmetal ion.

Example l Name the following binary ionic compounds.  NaCl Sodium chloride  Ca 3 P 2 Calcium phosphide

Example l Name the following binary ionic compounds.  PbOLead (II) oxide  SnBr 2 Tin (II) bromide

Problem l Name the following binary ionic compounds. Lead (IV) oxide  AlF 3 Aluminum fluoride  PbO 2

Problem l Name the following binary ionic compounds.  KClPotassium chloride  Na 3 N Sodium nitride

Writing Formulas for Binary Ionic Compounds l Write the symbol for the metal. Determine the oxidation number from either the column number or the Roman numeral and write it as a superscript to the right of the metal’s symbol.

Writing Formulas for Binary Ionic Compounds l To the right of the metal’s symbol, write the symbol for the nonmetal. Determine the oxidation number from the column number and write it as a superscript to the right of the nonmetal’s symbol.

Writing Formulas for Binary Ionic Compounds l Example: potassium fluoride K 1+ F 1-

Writing Formulas for Binary Ionic Compounds l If the two oxidation numbers add together to get zero, the formula is a one-to-one ratio of the elements.

Writing Formulas for Binary Ionic Compounds l Example: potassium fluoride K 1+ F 1- KF

Writing Formulas for Binary Ionic Compounds l Example: aluminum sulfide Al 3+ S 2-

Writing Formulas for Binary Ionic Compounds l If the two oxidation numbers DO NOT add together to get zero, you will need to “criss-cross” the superscripts. These numbers now become subscripts.

Writing Formulas for Binary Ionic Compounds l Example: aluminum sulfide Al 3+ S

Writing Formulas for Binary Ionic Compounds l Omit all positive and negative signs and omit all 1’s.

Writing Formulas for Binary Ionic Compounds l Example: aluminum sulfide AlS 23 Al 2 S 3

Problem l Lithium selenide l Write the formulas for the following binary ionic compounds. l Tin (II) oxide Li 2 Se SnO

Problem l Tin (IV) oxide l Write the formulas for the following binary ionic compounds. l Magnesium fluoride SnO 2 MgF 2

Ternary Ionic Compounds l Ternary ionic compounds are composed of at least 3 elements. l Name the metal ion, using a Roman numeral in parenthesis if necessary. l Follow this name with the name of the polyatomic ion.

Polyatomic ions l Polyatomic ions are groups of atoms that stay together and have a charge. l Examples include:  Nitrate NO 3 -1  Acetate C 2 H 3 O 2 -1  Hydroxide OH -1

Ternary Ionic Compounds l There is one polyatomic ion with a positive oxidation number (NH 4 + ) that may come first in a compound. Name the ion. l Follow this name with the name of the anion or second polyatomic ion.

Examples l Name the following ternary ionic compounds.  Li 2 CO 3  Al(OH) 3 Lithium carbonate Aluminum hydroxide

Examples l Name the following ternary ionic compounds.  (NH 4 ) 2 CO 3 Ammonium carbonate  GaPO 4 Gallium phosphate

Problems l Name the following ternary ionic compounds.  NaNO 3 Sodium nitrate  CaSO 4 Calcium sulfate

Writing Formulas for Ternary Ionic Compounds l Write the symbol for the metal or ammonium ion. Write the oxidation number as a superscript to the right of the metal’s/ammonium ion’s symbol.

Writing Formulas for Ternary Ionic Compounds l To the right of the metal’s symbol, write the symbol for the nonmetal or polyatomic ion. Write the oxidation number as a superscript to the right of the nonmetal’s/polyatomic ion’s symbol.

Writing Formulas for Ternary Ionic Compounds l Example: potassium nitrate K 1+ NO 3 1-

Writing Formulas for Ternary Ionic Compounds l If the two oxidation numbers add together to get zero, the formula is a one-to-one ratio of the elements.

Writing Formulas for Ternary Ionic Compounds l Example: potassium nitrate K 1+ NO 3 1- KNO 3

Writing Formulas for Ternary Ionic Compounds l Example: aluminum sulfate Al 3+ SO 4 2-

Writing Formulas for Ternary Ionic Compounds l If the two oxidation numbers DO NOT add together to get zero, you will need to “criss-cross” the superscripts. These numbers now become subscripts. l Parentheses are to be placed around polyatomic ions before criss-crossing.

Writing Formulas for Ternary Ionic Compounds l Example: aluminum sulfate Al 3+ SO ()

Writing Formulas for Ternary Ionic Compounds l Omit all positive and negative signs and omit all 1’s.

Writing Formulas for Ternary Ionic Compounds l Example: aluminum sulfate Al 2 (SO 4 ) 3

Problems l Write the formulas for the following ternary ionic compounds.  Ammonium chloride  Ammonium sulfide NH 4 Cl (NH 4 ) 2 S

Problems l Write the formulas for the following ternary ionic compounds.  Barium nitrate  Lead (II) carbonate Ba(NO 3 ) 2 PbCO 3