Ionic Bonding

Ionic Bonding Involves the transfer of valence electrons Attraction between a cation and an anion Cation Positively charged ion Typically metals But could be a polyatomic ion Anion Negatively charged ion Typically nonmetals But could be a polyatomic ion

Ionic Bonding

Ionic Bonding The oppositely charged ions are attracted to each other by a force called an ionic bond

Properties of Ionic Compound Most ionic compounds: Have high melting points Are hard and brittle Are soluble in water Form electrolytes (conduct electricity) when dissolved in water

Crystal Lattice Structure Ionic compounds form crystal lattices This explains why they have high melting points and are hard but brittle Na+ Cl-

Ionic Compounds in Water When ionic compounds dissolve, they separate into their ions The free ions can now move and conduct electricity

Representing Ionic Compounds Lewis Diagrams Formation of sodium chloride: Cl · · · ® Na+ [ ] Cl · · Na · +

Lewis Structures for Ionic Compounds Ba • O •• •• O Ba 2+ 2- Ba and O BaO Mg • Cl •• •• Cl Mg 2+ - 2 Mg and Cl Binary ionic compounds. Note the types of arrows used to move electrons – fishhooks for single e-. Write the Lewis symbol for each atom Determine how many e- each atom must gain or lose. Use multiples of one or both ions to balance the number of electrons. MgCl2

Representing Ionic Compounds Criss-Cross Method For monatomic ions: Take the absolute value of the ionic charge for the cation and make it the subscript for the anion and vice versa. Example: Al3+ and Cl- The 3 becomes the subscript for the chloride ion and the 1 becomes understood for aluminum. Forming aluminum chloride: AlCl3

Representing Ionic Compounds Criss-Cross Method For polyatomic ions: Additional step of including brackets around the polyatomic ion if it has a subscript other than one. Example: Mg2+ and OH- The 2 becomes the subscript for the hydroxide ion, but brackets are needed to indicate 2 of each the O and the H. The 1 becomes the understood subscript for Mg. Forming magnesium hydroxide: Mg(OH)2

Polyatomic Ions NICK the CAMEL ate a CLAM for SUPPER in PHOENIX Underlined letter represents the symbol of the element. The consonants represent the number of oxygen The vowels represent the negative charge. Eg. Underlined letter= N Number of consanants= 3 represents oxygens Number of vowels= 1 represents charge NO3- Nitrate

Practice Problems p. 68 #1,4 p. 71 #1-5 p. 73 #8-14 p. 74 #1-5