Ionic bonding occur(Review) Cations and anions attract each other because they have opposite charges. The force of attraction between the positively charged cation and the negatively charged anion creates the ionic bond. Ionic compounds can also be called salts.
What are Monatomic ions? One-Atom Ions See Page 218
What are Polyatomic ions? An ion made of two or more atoms. The charge is on the entire molecule. Example: OH - (hydroxide) See Page 221
What are Binary Ionic Compounds? These compounds contain only two types of elements. Example: Magnesium Oxide - MgO
What are some properties of Ionic Compounds? Very Strong Bonds High melting and boiling points. Solid at room temperature. Liquid and dissolved salts conduct electric current. Salts are hard and brittle.
Steps To Identify Ionic Compounds Step One: examine the substance. All ionic substances are solid at room temperature Step Two: tap the substance gently. All Ionic substances are hard and brittle Step Three: Heat a small sample of the substance. Ionic compounds generally have high melting points. Step Four: If the substance melts use a conductivity apparatus to determine if the substance conducts electricity. Step Five: dissolve the substance in water and use a conductivity apparatus to determine fi the substance conducts electricity.
Rules For Naming Ionic Compounds 1) Cation is the name of the element (if two or more ions are formed from this element roman numerals are used to indicate charge) Example: Cu 1+ (I)ion Cu 2+ (II) 2) Anion is formed for the name of the element, but it ends in –ide Example: Chlorine becomes Chloride Page 62
Practice Problems Name the following : NaCl – sodium chloride ZnS – zinc sulfide K 2 O – potassium oxide
Naming Compounds with Polyatomic Ions 1) Name the cation. 2) Name the anion (treat the entire polyatomic ion as one unit). Some Common Polyatomic Ions (pg 221)
Rules for Writing the Formula of an Ionic Compound 1) Write the symbols for the metal and the nonmetal. 2) Write the valences as superscripts above each symbol. 3) Drop the + and – signs. 4) Crisscross the valences so they become the subscript for the other element. 5) Reduce subscript whenever possible. Only when both are divisible by a number greater than one.
Practice Problems: Please turn to page 221 in text book. The teacher will give further instructions.