Section 12.1(A&B) Section 12.2 (All) Period 1 Group #1

Bonds Ionic bonding-oppositely charged ions –I–I–I–Ionic compound-metal and nonmetal Covalent bonding-electrons shared in nuclei Polar covalent bond-unequal sharing of electrons –S–S–S–Stronger attractions for shared electrons Ex. Hydrogen Fluoride (HF) H – F S + S¯

Questions 1. Compare the three types of bonding. 2. The unequal sharing of electrons is due to what type of attraction between elements?

Electro-negativity Unequal sharing between two atoms Increases left to right across the periodic table Decreases down a group Polarity of a bond depends on the difference between electro-negativity Higher electro-negativity means close electrons sharing values

Electro-negativity Table

Questions 1. How can you find the polarity of bonds? 2. Solve the polar bond of F- Au

Electron Configuration of Ions Representative metals form ions by losing electrons to achieve configuration of previous noble gases –Ex. Mg → Mg² + 2e- (Ne) 3s² - 2e- Nonmetals form ions by gaining electrons to achieve next noble gases –Ex. Br → Br (Kr) Cation and anion have end results of noble gases

Questions 1. H ow do representative metals form ions to achieve electron configurations? 2. S olve Fluorine (Fe) to achieve configuration.

Ionic compounds Ions packed specifically to maximize attraction –D–D–D–Described by a model with a closely packed ions as spheres Cation loses all valence electrons – becomes smaller Anion gains – becomes bigger

Model of Ionic Compound Cl- is the anion and Na+ is the cation

Review Questions 1. Why are cations smaller than an anions? 2. Explain why ions are formed in specific ways.

Polyatomic Ions Compounds contain polyatomic ions –charged species of several atoms Individual polyatomic ions held by covalent bonds –behave as unit free movement when dissolved in water

Polyatomic Ion Example NH4+ → ammonium nitrate and NO3- ions

Quiz ?’s 1. Shared electrons determine what type of bond? 2. Which area of the periodic table has the most electro-negativity? 3. How are the configurations of metals and nonmetals different? 4. Describe the model depicting the ions’ attraction. 5. What is the relationship between compounds and polyatomic ions?

Answers 1. Covalent bonds 2. The upper right corner 3. Metals form electron configurations of the previous noble gas while nonmetals form those of the next noble gas. 4. Tightly packed (hard) spheres; small ions occupy gaps formed by larger ions 5. Compounds contain polyatomic ions.

References 1/molecule/trans55.jpg 1/molecule/trans55.jpg abTutorials/PeriodicProperties/Ions/image s/ammonium3a.jpg abTutorials/PeriodicProperties/Ions/image s/ammonium3a.jpg mg/ionic_bonding5.gif