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Chapter 5 Types of Compounds. 5.1 Ionic Compounds 5.2 Molecular Substances. 5.1 Ionic Compounds - Objectives. Apply ionic charge to writing formulas for ionic compounds Apply formulas to name ionic compounds Interpret the information in a chemical formula.
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Chapter 5 Types of Compounds 5.1 Ionic Compounds 5.2 Molecular Substances
5.1 Ionic Compounds - Objectives • Apply ionic charge to writing formulas for ionic compounds • Apply formulas to name ionic compounds • Interpret the information in a chemical formula
Formula and Names of Ionic Compounds • Ionic compounds are composed of ions bound by ionic bonds usually a metal and a nonmetal • Ionic bonds are strong attractive forces • Ionic compounds are usually solids at room temperature • Many are crystalline • Difficult to melt high melting points • When melted or in solutions they conduct electricity
Binary Ionic Compounds • Binary compound- composed of two elements • Binary ionic compounds- composed of two different ions • NaCl • KI • CaF2
Ions • Positively charged = cation • When naming the name stays the same • Calcium ion • Sodium ion • Negatively charged = anion • When naming the name is changed • Ending becomes –ide • Chloride ion • Sulfide ion
Naming Binary Ionic Compounds • Always write the cation first followed by the anion. • Make sure the anion ending is modified to –ide. • Na+ + Cl- Sodium Chloride • K+ + I- Potassium Iodide
Writing Binary Ionic Compound Formulas • Compounds are always neutral • Net ionic charge must always be zero • Use subscripts to indicate when more than one ion of an element is present • When only one ion is present, no subscript is needed • NaCl • When more than one is present subscripts are need • CaF2 1 Calcium ion and 2 fluoride ions
Binary Ionic Compounds • Always written in the smallest whole number ratio – Formula Unit • Example Calcium Fluoride
Predicting Charges on Ions • Oxidation Number- the charge on the ion • Metals always lose electrons when they form ions • Nonmetals always gain electrons when they form ions • Periodic table can be used to predict the oxidation number (charge of ion) of some elements
Let’s Try It! • Write the formula for an ionic compound containing sodium and sulfur. • What is the name of the compound?
Write a formula for each of the following compounds • Lithium oxide • Calcium bromide • Sodium oxide • Aluminum sulfide
Write the formula & name for the compound formed from each of the following pairs of elements. • Barium and oxygen • Strontium and iodine • Lithium and chlorine • Radium and chlorine
Compounds Containing Polyatomic Ions • Polyatomic Ions-an ion that has two or more different elements • Group of atoms are covalently bonded together when the atoms share electrons • The individual atoms do not have a charge, but the group as a whole has an overall charge
Polyatomic Ions • Ionic compounds may contain positive metal ions bonded to negative polyatomic ions or negative nonmetal ions bonded to positive polyatomic ions
Writing formulas using Polyatomic Ions • Treat the polyatomic ion as one unit or a single ion • Write the cation ion first followed by the anion • When more than one polyatomic ion is needed to make the net charge zero you place it in parentheses and then add the subscript.
Naming Polyatomic Ions • Follows the same rules as naming binary • Name the cation first and then the anion • You do not change the ending of the anion for polyatomic ions • -ite indicates one less oxygen atom than -ate • -ate indicates one more oxygen atom than –ite • Does not tell you the number of oxygen atoms in the ion
Let’s Try It! • Write the formula for the compounds made from each of the following ions. • Ammonium and sulfite ions • Calcium and hydrogen phosphate ions • Ammonium and dichromate ions • Barium and nitrate ions
Let’s Try It! • Write the formula for each of the following compounds. • Sodium phosphate • Magnesium hydroxide • Ammonium phosphate • Potassium dichromate
Compounds of Transition Elements • Transition elements are groups 3 through 12 in the periodic table • Form positive ions, but they form more than one type of positive ions • Copper forms two ions one with a +1 charge and one with a +2 charge • The way they are distinguished is with roman numeral. Copper (I) and Copper (II)
Let’s Try It! • Write the formula for the compounds made from each of the following pairs of ions. • Copper (I) and sulfite • Tin (IV) and fluoride • Gold (III) and cyanide • Lead (II) and Sulfide
Let’s Try It! • Write the names of the following compounds. • Pb(NO3)2 • Mn2O3 • Ni(C2H3O2)2 • HgF2
Hydrates • Many ionic compounds are prepared by crystallization from a water solution, and water molecules become a part of the crystal. • Hydrates- a compound in which there is a specific ratio of water to ionic compound. • In hydrate, the water molecules are chemically bonded to the ionic compound
Hygroscopic • Hygroscopic- a substance that absorbs water molecules from the air to become a hydrate. • Sodium Carbonate • Some substances are so hygroscopic that they take up enough water from the air to dissolve completely and form a liquid solution. These compounds are called deliquescent. • Sodium Hydroxide
Writing Formulas for Hydrates • When writing a formula for a hydrate you place a dot in the formula between the ionic compound and the water. • CaSO4· 2H2O • What this means is for every one calcium sulfate there are two water molecules in the hydrate.
Naming Hydrates • You use the regular name for the compound followed by the word hydrate, to which a prefix is added. • 1 = mono- • 2 = di- • 3 = tri- • 4 = tetra- • Exp.: CaSO4· 2H2O Calcium sulfate dihydrate
Anhydrous • Anhydrous – a compound in which all the water has been removed, usually by heating • In some cases the anhydrous compound may be a different color than the hydrate. • Copper (II) sulfate pentahydrate is blue compound when it is heated to remove the water and become anhydrous it turns white, this compound is Copper (II) sulfate anhydrous
Homework • P. 184-185 #1-5, 7, 8