Chapter 8 Ionic Compounds Formation of Ions ► Which type of elements are the most stable (least willing to undergo change)? ► How many valence electrons do they have? ► What would you expect of the other elements to increase their stability? Octet Rule ► Octet Rule- atoms gain, lose, or share ein order to acquire a full set of 8 valence e-. Ex. sodium ►A sodium ion is more stable than the neutral sodium atom because it now has 8 valence e-. Ions ► Cation ► Anion ► Charge –written as superscript Chemical Bonds ► Chemical bond- an attraction (force) between atoms that holds them together 3 Types of Bonds 1. Nonpolar covalent bond- Valence electrons are shared equally between bonded atoms 2. Polar covalent bond- Valence electrons are shared unequally between the bonded atoms. 3. Ionic bond- Valence electrons are transferred from one atom to another, forming ions. These oppositely charged ions attract holding ionic compounds together. Ionic Bonds ► Ionic compound – compound made up of + and - ions that combine to be neutral consists of a metal and nonmetal or a compound with a polyatomic ion. Formation of Ionic Cmpds. ► Formation of ionic compounds-compounds form to get 8 valence e- Using electron-dot notation Ex. Na and Cl to form Na+ and Cl- = Ex. Al and Cl to form Al+3 and Cl- = ► Formula unit-Simplest ratio of the ions represented in an ionic compound Ex. MgCl2 Subscripts –number of atoms in a compound Binary Ionic Compounds Binary ionic compounds are composed of a metal cation and a nonmetal anion. Steps writing Ionic Chemical Formulas: 1. Write symbol and charge of positive ions first. 2. Write symbol and charge of negative ion next. 3. Use subscripts if more than one ion is needed to make the total charge of the cmpd zero. Reduce ratio if possible. Write the chemical formulas for the following compounds: 1. 2. 3. 4. 5. 6. sodium chloride aluminum sulfide manganese (II) nitride magnesium nitride zinc oxide lead (IV) phosphide Naming Binary Ionic Cmpds. Name cation, roman numeral, name anion (if needed) Using Roman Numerals Ions with multiple charges: Transition metals and metals in group 4A of the periodic table often have more than one charge. (Exception zinc, silver, cadmium) Examples: 1. CaCl2 2. Ba3N2 3. PbO2 4. Na2O 5. MnN 6. GaI2 7. SnCl4 Polyatomic Ions ► Polyatomic ions-an ion made up of more than one element -the ion with more oxygen atoms use the suffix –ate -the ion with less oxygen atoms use the suffix –ite Polyatomic Ions Ionic compounds with polyatomic ions: ► Charge applies to entire group of atoms ► Polyatomic ions act as individual ions so you can write chemical formulas the same way as binary compounds. Examples: 1. Ammonium chloride 2. Aluminum carbonate 3. Calcium phosphate 4. Iron(III) perchlorate Polyatomic Ions Naming ionic compounds with polyatomic ions 1. Name the cation first, followed by the anion. Use roman numerals when necessary. 2. If the compound contains a polyatomic ion, simply name the ion. Examples: 1. CaCO3 3. Al(ClO3)3 2. NH4Cl 4. CoCO3 Properties of Ionic Cmpds. Properties of Ionic Compounds: ► Crystal lattice-3-D geometric arrangement of particles that is formed because of a strong attraction of positive ions and negative ions in an ionic compound ► High melting points and boiling points, and high degree of hardness-Because the bond is very strong, it takes a lot of energy to break apart the bond Properties of Ionic Cmpds. ► Ionic compounds are brittle ► Electrolyte-Ionic compounds dissolved in liquids are good conductors of electricity because the ions are free to move ► Energy changes occur when ionic compounds form A positive ion to a negative ion is always exothermic. Lattice energy-energy needed to separate the ions of the ionic compound. (Strength of holding ions). The more negative the number, the stronger the bond. Naming Binary Acids Acid-A compound that produces hydrogen ions in solution (hydrogen in front). 2 types of acids: binary acids and oxyacids Anion ending -ide -ate -ic Acid name hydro ___ ic acid ____ ic acid ____ ous acid Naming Acids Examples: 1. HCl 2. H2CrO4 3. HBr 4. HClO3 5. H3P 6. H2S 7. H2SO4 Formulas for Binary Acids Examples: 1. Hydrosulfuric acid 2. Nitric acid 3. Hydrofluoric acid 4. perchloric acid 5. Hydronitric acid 6. Sulfurous acid Metallic Bonding Metallic bonding-bonding due to attraction between metal atoms and a sea of electrons. Explain these properties with bonding concept. ► Malleability-metals can be hammered in sheets. ► Ductility-metals wires can be drawn into ► Boiling points- atoms must be separated from the group of cations and electrons ► Good conductors-movement of mobile electrons around positive cations Alloys Alloys-mixture of elements that has metallic properties 2 types of alloys 1. Substitutional Alloy- Atoms of the original metallic solid replaced by other metal atoms of similar size. 2. Interstitial Alloy -The small holes in a metallic crystal are filled with smaller atoms