1. CHEMISTRY October 19th, 2011

2. Welcome Back! October 19th, 2011 • Brainteaser: • Let’s reflect on last quarter’s performance: • What are some things you thought you did well for this class? • What are some things you think you could improve for this quarter? • What is your overall goal for this quarter (i.e. what do you want to accomplish this quarter and how are you going to do it?)

3. Agenda • Brainteaser • Unit 5: Ionic Bonding Notes • Homework • Ionic Bonding Practice Worksheet

4. Unit 4: Chemical Bonding • Bonding • Differences in chemical behavior are due to differences in the types of bonds • Bond: forces that hold atoms together in molecules or ionic compounds.

5. Chemical Bonding • Types of bonds and types of substances • Ionic • Covalent • Metallic • The type of bond between atoms is partially responsible for the properties of the substance.

6. Chemical Bonding • Bonding • Involves the valence electrons or outermost shell (or highest shell) electrons • For group A elements – the group number tells how many valence electrons • For example: • K, Ca, C, B, N, F, Ne • Lewis Dot Structures show the valence electrons around an atom and for most molecules and compounds a complete octet for the elements is needed. • For example: N, Al, H2O

7. Lewis Dot Structures • These symbols are called Lewis symbols  • We generally place the electrons on four sides of a square around the element symbol.

8. Drawing Lewis Dot Structure • Place DOTS around the SYMBOL clockwise pairing up dots on the second time around • For example: • Magnesium (Mg) and Oxygen (O)  MgO Mg O

9. Ionic Bonding

10. Ions and Ionic Compounds • Ions are formed by adding or subtracting electrons from a neutral atom or molecule. • Cation: positively charged ions (remove e-) • Anions: negatively charged ions (add e-) • Names!!

11. Two Types of Ions • Monatomic ions • Single atom ions • O 2- • Na+ • Al3+ • Polyatomic ions • More than one atom ions • NH4+ • OH – • SO42-

12. Predicting Charges of Ions • Electron Counts of Stable Ions • Ions tend to have the same number of electrons as the nearest noble gas. • Transition metals are not as predictable, but +2 and +3 are common.

13. Main Group Elements Note periodicity of charges

14. Transition Elements • Not periodic; +2 and +3 common

15. Charges and Formulas of Oxoanions • Oxoanions generally have the same charge as the simple anion of the same nonmetal. Related to position in the periodic table; note exceptions for B, C, N Polyatomic Ions tend to reflect the charge of the base element

16. Ionic Bonds form when… • A cation (metal) bonds with an anion (nonmetal) • A salt is formed: • For example: Sodium: Na “metal” bonded to Chlorine: Cl “nonmetal” • For example: Magnesium: Mg “metal” bonded to Chlorine: Cl “nonmetal”

17. Ionic Bonding:The Formation of Sodium Chloride • Sodium has 1 valence electron • Chlorine has 7 valence electrons • An electron transferred gives • each an octet Na:1s22s22p63s1 Cl:1s22s22p63s23p5

18. Ionic Bonding:The Formation of Sodium Chloride This transfer forms ions, each with an octet: Na+1s22s22p6 Cl-1s22s22p63s23p6

19. The resulting ions come together due to electrostatic attraction (opposites attract): The resulting ions come together due to electrostatic attraction (opposites attract): The resulting ions come together due to electrostatic attraction (opposites attract): The resulting ions come together due to electrostatic attraction (opposites attract): Cl- Cl- Na+ Na+ Na+ The net charge on the compound must equal zero The net charge on the compound must equal zero

20. Ionic bond Example Lewis Dot diagram A positively charged ion is attracted to a negatively charged ion. A transfer of electrons Metal and a Non-Metal NaCl Na Na Na Na Cl Cl Cl Na Na Cl Lewis Dot Drawing • A positively charged ion is attracted to a negatively charged ion. • A transfer of electrons • Metal and a Non-Metal • NaCl • A positively charged ion is attracted to a negatively charged ion. • A transfer of electrons • Metal and a Non-Metal • NaCl

21. Practice • Draw the Lewis dot structures for the following compounds: • CaO • BaCl2 • Na2S

22. Crisscross Method Example: Ca and F Write the element symbols for the cation and anion, with the cation on the left and the anion on the right. Write each ion’s charge as a superscript. Crisscross the two charges moving them downward diagonally from one superscript to the other subscript. Writing Formulas for Ionic Compounds

23. Practice • Write the correct formula for the ionic compounds composed of the following pairs of ions using the crisscross method: • Potassium and iodide • Magnesium and chloride • Aluminum and bromide • Cesium and nitride • Barium and sulfide • Iron (II) and fluoride

24. CHEMISTRY October 20th, 2011

25. Warm Up • Write the correct formula for these ionic compounds: • Aluminum oxide • Barium nitride • Iron (III) oxide • Magnesium carbide

26. Agenda • Brainteaser • Grade Homework: Practice W/S • Unit 5 Notes: • Naming Ionic Compounds • Properties of Ionic Compounds • Partner Bonding Activity • Homework: • Naming Ionic bonds W/S

27. Naming Ionic Compounds • Step 1: • Cation is written first in the name; anion is written second in the name • Name of cation is the same as the neutral atom element (Na+ = Sodium) • Step 2: • Anion is written by adding the suffix –ide to the root of the element name (I- = iodide) • For example: NaCl = Sodium Chloride, Al2O3 = Aluminum oxide • Step 3: • Figure out if you need a Roman numeral in the name (transition metals). • Figure out what the Roman numeral should be • For example: Fe2O3 • Step Four: Check your work

28. PracticeNaming Ionic Compounds • KF • AlF3 • KCl • Na3P • Fe2O3

29. Properties of Ionic Bonding • Definition: • In an ionic bond, a positively charged ion is attracted to a negatively charged ion • Electrostatic Attraction

30. Properties of Ionic Bonding • Solid at room temperature • Electrical conductivity • Conducts electricity when dissolved in water or in liquid (molten) form • Dissociated ions can carry charge through the solution • Hardness • Hard but brittle • Electrostatic repulsion • Melting points and Boiling points • High melting and boiling point • Forces of attraction between positive and negative ions are strong

31. Properties of Ionic Bonding

32. Quiz • Write the chemical formula for these ionic compounds: • Sodium bromide • Potassium nitride • Beryllium phosphide • Write the chemical names for these ionic compounds • SrCl2 • MgI2 • Ba3N2