1. Monday November 12, 2012 (WS - Building and Naming Ionic Compounds)

2. Write the formulas for the chemical compounds that are formed when the following atoms bond: sodium and chlorine NaCl magnesium and bromine MgBr 2 calcium and oxygen CaO aluminum and sulfur Al 2 S 3

3. Announcements

4. Assignment Currently Open Summative or Formative? Date IssuedDate Due Date Into GradeSpeed Final Day QUIZ 9S610/26 11/16 QUIZ 10S711/2 11/16 WS – Covalent Bonding F1411/711/16 QUIZ 11S111/9 11/30

5. Chemical Compound Formation and Naming

6. A chemical formula indicates the types of atoms and relative number of each type of atom in a chemical compound. Chemical Formulas

7. For an ionic compound, the chemical formula reveals the ratio of ions of each element contained in the ionic matrix. Al 2 O 3 In the ionic compound aluminum oxide, there are 2 ions of aluminum for every three ions of oxygen in the ionic matrix.

8. Monoatomic Ions Ions are created when a neutral atom loses or gains electrons in the process of becoming stable. The atom no longer has equal numbers of protons (+) and electrons (-). Monoatomic ions (meaning “one atom”) are ions formed from a single atom. H + Ca 2+ Cl - O 2-

9. Polyatomic Ions Polyatomic ions (meaning “more than one atom”) are ions formed from multiple atoms bonded into a group. NH 4 + Hg 2 2+ OH - SO 4 2- Notice that the number 1 is not shown.

10. Chemical Formulas For an ionic compound made with one or more polyatomic ions, the chemical formula still reveals the ratio of ions, whether they are monoatomic ions or polyatomic ions. Al 2 (SO 4 ) 3 In the ionic compound aluminum sulfate, there are 2 ions of aluminum for every three ions of sulfate in the ionic matrix.

11. Cations and Anions When atoms lose electrons, they now have more protons (+) than electrons (-), and take on the + charge of the extra protons. Positively charged ions are called “cations.” K+ NH 4 + Br - OH - When atoms gain electrons, they now have fewer protons (+) than electrons (-), and take on the - charge of the extra electrons. Negatively charged ions are called “anions.”

12. Oxidation Numbers Oxidation numbers (the green numbers above the main-block groups on the larger Periodic Table on the right) indicate the charge on that atom’s ion after it has lost or gained electrons in the process of becoming stable. Na + Mg 2+ Al 3+ C 4+/- Mg 2+ N 3- O 2- F -

13. Oxidation Numbers Oxidation numbers can be used to determine the ratio in which atoms will bond to one another when forming chemical compounds. This procedure is illustrated on the next slide.

14. “Crossing” oxidation numbers is a method of balancing the charges between ions in an ionic compound. For example: If an aluminum ion is bonding with an oxygen ion: Al 3+ + O 2- Al 2 O 3 Crossing Oxidation Numbers Notice that you do not cross the + and – charge signs, only the numbers of the charges.

15. It is also important to remember that the positively- charged cation is always listed first in the chemical formula, followed by the negatively- charged anion. Crossing Oxidation Numbers Therefore: Na + Cl - Never: Cl - Na +

16. Oxidation Numbers In general, follow this system for determining an elements oxidation number: Group 1 = 1 + (+) Group 2 = 2 + Group 13 = 3 + Group 14 = 4 +/- Group 15 = 3 - Group 16 = 2 - Group 17 = 1 - (-) Group 18 = 0 Since the d-block Transition Metals (Groups 3-12) have variable oxidation states, their oxidation numbers will be listed as a Roman numeral. Ex) Fe (III) = Fe 3+

20. Binary Ionic Compounds Binary ionic compounds are compounds composed of two different elements. In a binary ionic compound, the total numbers of positive and negative charges must be equal.

21. Example Magnesium and bromine combine to form magnesium bromide. Mg 2+ + Br - → MgBr 2 It takes 2 Br - anions, each with a 1 - charge to balance Mg with its 2 + charge! Binary Ionic Compounds

22. Naming Monoatomic Ions Monoatomic cations are identified simply by the element’s name.

23. Naming Monoatomic Ions When monoatomic anions are bonded into compounds, their names are changed to end in –ide

24. Naming Polyatomic Ions The names of polyatomic ions are never changed as they are bonded into compounds. Example Na + NO 3 æ NaNO 3 sodium + nitrate æ sodium nitrate

25. Polyatomic Ions Handout: Reference Sheet - Polyatomic Ions

26. Worksheet Building and Naming Ionic Compounds