1. Chapter 9 Notes, part I Writing Ionic Formulas

2. Compounds Up until now, we have only looked at single elements. There are only (to date) just over 100 elements, so how do we account for there being so many different types of stuff?

3. Compounds There are millions of different compounds—two or more elements that are combined chemically. The two types of compounds we will discuss in this chapter are ionic compounds and covalent compounds.

4. Ionic Compounds Last chapter we discussed ions— elements that have a charge due to losing or gaining electrons. Ionic compounds are made of ions.

5. Ionic Compounds Metals tend to form ions by losing electrons, giving them an overall positive charge. These are called cations. Nonmetals tend to form ions by gaining electrons, giving them an overall negative charge. These are called anions.

6. Ionic Compounds An ionic compound is formed from a cation and an anion, which means they are usually formed from a metal and a nonmetal.

7. Ionic Compounds Anions and cations can also be made up of a group of elements bonded together that carry an overall charge. These groups of elements are called polyatomic ions.

8. Ionic Compounds Even though an ionic compound is made from charged particles, it is still electrically neutral. This means that its total charge is always EQUAL TO ZERO!!!

9. Chemical Formulas SIDENOTE: The smallest part of an ionic compound is called a formula unit—just like the smallest part of an element is called an atom. A chemical formula is like the recipe of a compound—it tells you the type and number of each element in the compound.

10. Writing Chemical Formulas 1) Write the symbol for the elements and their oxidation number, positive ion first (the metal). EX: For a compound of Magnesium and Chlorine Mg +2 Cl

11. Writing Chemical Formulas 2) Criss cross the numbers and write them as subscripts without the signs. Mg Cl +221

12. Writing Chemical Formulas 3) If there is a one charge, do not write it. Mg 1 Cl 2 Mg Cl 2

13. Writing Chemical Formulas 4) If you have subscripts that are multiples, reduce them down. PbO +4-242 2 1

14. Writing Chemical Formulas 5) If using polyatomic ions, put parentheses if there are more than one. CaNO 3 +221 ()

15. Writing Chemical Formulas Here’s an example of a polyatomic that doesn’t have parentheses. NaPO 4 +1-313

16. Practice These: Barium and chlorine Rubidium and nitrogen Lithium and phosphate Iron (III) and nitrate Manganese (IV) and sulfur BaCl 2 Rb 3 N Li 3 PO 4 Fe(NO 3 ) 3 MnS 2

17. Naming Ionic Compounds

18. For ionic compounds where the metal always has the same oxidation number, 1) Name the metal. EX: BaBr 2 Barium

19. Naming Ionic Compounds For ionic compounds where the metal always has the same oxidation number, 2) Write the name of the non-metal, and change the end to –ide. Barium brom ine ide EX: BaBr 2

20. Naming Ionic Compounds If there is a polyatomic anion, then you do not change the ending: EX: Ca(NO 3 ) 2 Calcium nitrate

21. Name These: Na 2 O MgCl 2 Na 2 CO 3

22. Naming Ionic Compounds 3)If a positive ion (a metal) can have more than one oxidation number, you have to designate its charge in the name! We do this by putting the charge as a roman numeral in parenthesis between the positive and negative ion.

23. Naming Ionic Compounds Why do we need to do that? Name: Fe 2 O 3 FeO These both exist in nature, so we have to show which one we mean.

24. Naming Ionic Compounds Fe 2 O 3 Name it: Iron ox ygen ide ( ) III -2 If this is true, then what was iron to begin with? +3 Reverse criss cross to find the charge of the iron:

25. Naming Ionic Compounds Fe O Name it: Iron ox ygen ide ( ) II If this is not true, the numbers must have been reduced. +2-2

26. Naming Ionic Compounds Metals that don’t need parentheses: Group I, II and IIIA Zn, Cd (always +2) and Ag (always +1) Which means transition, inner transition and other metals do!

27. Naming Ionic Compounds Final flowchart of how to name: Name the positive ion. Does it need a roman numeral? If so, reverse criss cross, if not, ignore. Name the negative ion and: If a nonmetal end in -ide; if not, end normally

28. Name these: Na 2 S CuCl 2 K 2 SO 4 Pb(NO 3 ) 4