Classification of Compounds

Classifying Pure Substances Last class: Classification of elements into metals nonmetals metalloids This class: Classification of Compounds

Three classes of Compounds 1)Metal-nonmetal: Ionic compounds 2)Nonmetal-nonmetal: Molecular compounds AKA Covalent compounds 3)Metal-metal: Alloys Example of Alloys: Brass = Cu 5 Zn 8

Empirical Classification of Ionic and Molecular Compounds Identifying ionic compounds and molecular compounds: -divided by their properties. -leads to an empirical definitions of both groups Diagnostic Tests: A lab procedure. Using easy to obtain properties that are different between inorganic and molecular (organic) compounds to identify compounds.

Examples of Diagnostic Tests -Using acid base indicators -Cobalt chloride paper changes from blue to pink if it comes in contact with water. -Hydrogen makes a popping sound when it comes into contact with a flame -Oxygen gas will relight a snuffed out match

Empirical Definitions of Compounds Empirical Definition: List of empirical properties that define a class of chemicals Ionic Compounds: -Solid at standard atmospheric temperature and pressure (SATP). -When dissolved in water they conduct electricity

Empirical Definitions of Compounds Molecular Compounds: -Solid, liquid or gas at standard atmospheric temperature and pressure (SATP). -When dissolved in water they do not conduct electricity

Empirical Definition of Acids Acids are a group of compounds that have characteristics of more than one class Characteristics of… Organic (molecular) compounds: Acids are composed of nonmetal elements. Ionic compounds: Acids conduct electricity

Empirical Definition of Acids Acids: -Solids, liquids or gases (at SATP) -Conduct electricity when dissolved in water -Turns blue litmus paper red

Empirical Definition of Bases Bases: Turns red litmus paper blue. Neutral Compounds: Do not change the color of either red or blue litmus paper.

Binary Ionic Compounds The first class of ionic compounds -Binary ionic compounds: Made of 2 kinds of atoms (2 kinds of monatomic ions) Eg. NaCl Made from Na cation (Positively charged ion) and a Cl anion (Negatively charged ion)

Ionic Compounds Empirical Formula of Ionic Compounds: Made by measurements taken 1)by combining elements into compounds 2)by chemically decomposing compounds into elements

Balancing Charges How do we explain the empirically determined ionic formula for compounds? 1)Predict the charges on an ion based on atomic theory 2)Balance the charges of the ions that you are combining by multiplying Eg. Al = 3+Cl = 1- Al = 3+ 3 xCl = 3- Tells you that 3 Cl ions are needed in the formula AlCl 3

Explaining Polyatomic ions Not all ions were monatomic = New class of ionic compounds  Polyatomic ions (Poly = more than 1) Use the same steps as binary ionic compounds to find chemical formula

Explaining Multivalent Ions Multivalent ions: Valent = valence shell or outer most ion shell Multi = more than one Result: They have more than one possible number of electrons on their outer shell Eg. Cu 2+ Versus Cu 3+ Cu 2+ = Has 2 electrons on the outer shell Cu 3+ = Has 3 electrons on the outer shell

Hydrates Hydrates: Decompose at low temperatures to produce water along with another compound. The water acts like part of the compound not as a solvent Eg. Bluestone: CuSO 4. 5H 2 O = Blue crystal Heat to evaporate water = CuSO 4 = White powder

Summary Table mixes to hydrates