Naming Compounds

1. Naming Compounds Unit D.5

2. Part 1: Ionic Compounds

3. Ionic Formulas • An ionic compound formula is a ratio of the number of cations to anions • E.g.: CaCl2will have 1 Calcium atom per 2 chlorine atoms • The ratios are determined by the charge of each atom • Calcium has a +2 charge, so there needs to be two chlorine atoms per atom of calcium -1 +2

4. For the visual learners out there…

5. Here’s Calcium Chloride

6. Balancing Ionic Formulas: Crisscross Method 1. Write the charges of each atom based upon its location in the periodic table Ca + Cl 2+ -1 1 2 2. Bring the numbers down diagonally, ignoring the sign = CaCl2 3. Reduce to smallest possible ratio, if necessary. Remove redundant numbers.

7. Practice MgO • Mg + O . • Na + S ______________ . • Sr + Cl . • Be + O _______________ • Li + F . Na2S SrCl2 BeO LiF

8. Naming Ionic Compounds • Number of atoms does not affect naming • The regular name of the metal cation always comes first • The suffix of the anion changes to –ide • NaCl = Sodium Chloride • NaF = Sodium Fluoride • CaBr2 = Calcium Bromide

9. Common Anions

10. Try these. • Na2S • Li3N • Ag2O • CaBr2 • K2O • SrCl2 Sodium Sulfide ________________ ________________ ________________ ________________ ________________ ________________ Lithium Nitride Silver Oxide Calcium Bromide Potassium Oxide Strontium Chloride

11. Ions with multiple charges • Transition metals can have different ionic states • Iron, for example, can sometimes have a +2 charge, while other times it will have a +3 • To avoid confusion, we notate Iron with a +2 charge as Iron(II), while Iron with a +3 charge would be Iron(III)

12. Demo • Iron(III) Oxide = Fe3+ + O2- = Fe2O3 Iron(II) Oxide = Fe2+ + O2- = FeO

13. Now try these • FeO ______________ • Fe2O3 _____________________ • NiBr3 _____________________ • CrO ______________ • Cr2O3 _____________________ Iron(II) Oxide Iron(III) Oxide Nickel(III) Bromide Chromium(II) Oxide Chromium(III) Oxide

14. Writing Formulas from Names • Use periodic trends to predict ionic charges of atoms (Group I = +1, Group II = +2, etc) • Overall charge of compound should equal 0 • Use the “crisscross method” to assign number of atoms & reduce to lowest # ratio • “Sodium Fluoride” = Na+ + F- = • “Calcium Chloride” = Ca2+ + Cl- = NaF CaCl2

15. Practice • Calcium Bromide • Potassium Sulfide • Nickel(II) Iodide • Copper(II) Oxide • Strontium Fluoride

16. Polyatomic ions • Some molecules have an overall charge, like ions • These are called polyatomic ions • They are treated as a single unit and can NOT be separated! • Naming system is otherwise the same Barium Sulfate

17. Balancing polyatomic ions Treat the entire polyatomic ion as 1 unit Al+3 + SO42- ( ) 2 3 Al2(SO4)3 For balancing, place the polyatomic anion in parenthesis Aluminum Sulfate Naming Conventions are the same as regular ions

18. Balance and name the following using Na2SO4 Sodium Sulfate • Na + SO42- _______________________ • Ca + OH- _______________________ • Mg + NO3- _______________________ • Sr + CO32- ______________________ • NH4+ + NO3- ______________________ Ca(OH)2 Calcium Hydroxide Mg(NO3)2 Magnesium Nitrate SrCO3 Strontium Carbonate NH4NO3 Ammonium Nitrate

19. Naming Covalent Compounds • Number of atoms is represented by prefix • All atoms in a molecule have their own separate prefixes and are listed in order of appearance • First element only has a prefix if it is greater than 1 • Last element ends in -ide

21. Practice • CO ____________ • NO2 __________________ • SF2 __________________ • CCl4 __________________ • NI3 __________________ Carbon Monoxide Nitrogen dioxide Sulfur difluoride Carbon tetrachloride Nitrogen triiodide

22. Naming Acids • All* Acids begin with Hydrogen • HCl, H2SO4, HNO3, etc • Although there is a naming system, most scientists just memorize them