Ionic Bonding, Metallic Bonding and Compound Naming Chapters 7 and 9

Ionic Compounds The chemical formula for an ionic compound is called a formula unit which represents the lowest who number ration of atoms in that compound.( ex. NaCl) Ionic bond formation begins by the transfer of electrons from metal to non-metal atoms Cations and anions are electrostatically attracted to eachother, completing the ionic bond Coordination Number = The number of ions of opposite charge surrounding the ion in a crystal.

Comparing Properties of Ionic and Covalent Compounds Ionic CompoundsCovalent Compounds Crystalline solids at room temperature High melting points Most are water soluble Conduct electricity when dissolved in water or molten Gases or brittle solids at room temperature Low melting points Only polar covalent compounds dissolve in water Do not conduct electricity

The Octet Rule - Metals Metals tend to lose electrons to gain stability. When they lose electrons they attain a stable electron configuration where the next lowest-energy level has a full octet.

The Octet Rule – Non-metals Non-metals tend to gain electrons to obtain a full octet in their highest occupied p sublevel

Formation of Ionic Compounds Cations and anions combine to form ionic compounds + + NaCl

The Formation of Calcium Chloride CaCl 2

Metallic Bonding Positive metal ions floating in a sea of electrons. Metals are excellent conductors of electricity Metals can be easily deformed (They are malleable and ductile) Know that metals are arranged in crystalline structures, but do not worry about the arrangement of these structures: face-centered, body-centered, hexagonal.

Alloys Alloys are mixtures of metals Properties of alloys are usually superior to those of their component elements. Substitutional AlloyInterstitial Alloy

Naming Binary Ionic Compounds Rules The first element (always the metal) takes its name The name of the second element (always non-metal) is changed by dropping its ending and adding –ide. Element Name Element Name C Carbide S Sulfide N Nitride Cl Chloride O Oxide Se Selenide F Fluoride Br Bromide P Phosphide I Iodide Example: BaCl 2 (Barium Chloride) *Notice that no prefixes are used in the naming of these compounds

Writing Formulas for Binary Ionic Compounds Determine the charge on the cation based on the number of electrons lost from the neutral atom. Determine the charge on the anion based on the number of electrons gained by the neutral atom. Determine the cation to anion ratio required to create a neutral compound, keeping in mind that the formula unit represents the lowest whole number ratio of atoms. NameCationAnionCompound Sodium SulfideNa + S 2- Na 2 S Calcium oxideCa 2+ O 2- CaO

Naming Ionic Compounds with Stock System Ions Some atoms multiple oxidation numbers (numbers of electrons that can be lost from the neutral atom) When naming compounds made with these ions, the oxidation number is noted in the compound name using roman numerals (I, II, III, IV, V, VI) FormulaCationAnionName CuClCu + Cl - Copper I Chloride CuCl 2 Cu 2+ Cl - Copper II Chloride

Naming Compounds Containing Polyatomic Ions Rules The first element always takes its name. Remember to use the roman numerals for atoms that have multiple oxidation numbers. There is one common polyatomic cation (Ammonium ion NH 4 + ) The non-metal portion of the ionic compound is polyatomic and each ion has a special name. Oxyanions are polyatomic ions that contain oxygen. Two oxyanions with the same two elements (one of which is always oxygen) will have end in -ate or –ite. The –ate ion will always have one more oxygen than the –ite ion. Example: Sulfite SO 3 2- Sulfate SO 4 2-

Writing Formulas for Compounds Containing Polyatomic Ions Polyatomic ions are a cluster of atoms that carry a charge. The same procedure that is used for binary compounds is applied to compounds containing polyatomic ions. The ultimate goal is to create a compound that has a neutral charge. NameCationAnionCompound Lithium phosphateLi + PO 4 3- Li 3 PO 4 Aluminum dichromateAl 3+ Cr 2 O 7 2- Al 2 (Cr 2 O 7 ) 3

Naming Acids There are two kinds of acids – Binary Acids and Oxyacids Binary acids are the combination of H + and a monatomic anion. The name of a binary acid always begins with the prefix hydro- and ends with the suffix –ic. Example:HCl (hydrochloric acid) exception: hydrocyanic acid (HCN) Oxyacids are the combination of H + and a polyatomic anion containing oxygen (-ate and –ite ions). The name of an oxyacid acid always ends in –ic or –ous. Example: H 2 SO 4 (sufuric acid) vs. H 2 SO 3 (sulfurous acid) Notice that the prefix hydro- does not appear in the name of oxyacids

Laws Governing Formulas and Names Law of Definite Proportions A chemical formula indicates the ratio of atoms of each element in the compound This law states that in samples of an chemical compound, the masses of the elements are always in the same proportion. Law of Multiple Proportions Multiple compounds can contain the same atoms in different proportions. Keeping the mass of one atom in each compound constant, the ratio of remaining atom in each compound will be a small whole number.