Ionic Compound Properties, Lewis Dot Structures & Polyatomics

1. Ionic Compound Properties, Lewis Dot Structures & Polyatomics Mr. Shields Regents Chemistry U09 L02

2. Ionic compounds form Crystalline structures of alternating atoms forming geometric patterns Multiple repeating units Are the basis of crystal formation

3. The Formula unit of an ionic compounds can go On an indefinite no. of times, for example NaxClx When we write NaCl We are using what is known As anEmpirical formula i.e. the formula unit. Many natural Gems such as Rubies, saphires And emeralds have unique crystalline patterns Based on Al2O3

4. Sapphires & Rubies Emeralds

5. Properties of IONIC Compounds

6. Conductivity of Ionic compounds When ionic compounds Are dissolved or melted The crystal lattice breaks Down. In the crystal lattice ions are not free to move. When dissolved or molten these ions can move. - If a voltage is applied cations will flow to one electrode and anions will flow to the other - this movement of ions means there is a flow flow of electricity

7. 2- [ O ] Lewis dot structures • What does the lewis dot structure of an ionic compound • look like? • For CATIONS (+) we draw the ion with only the symbol & charge & sometimes with Brackets Na+ ( or [Na]+ ) Fe3+ • For ANIONS we draw the ion with its valence electrons enclosed in brackets and the charge indicated outside the brackets

8. Lewis dot structures Writing Lewis dot structures for Ionic compounds follow the Same rules with some additions • The Cation (+) is written first • The Anion (-) is written second • Number of ions are specified as a prefix in front of brackets OR the ion is written twice.

9. Ca2+ 2 - 2- 2- - - - [Na]+ K+ [ Br ] [ Br ] [ Br ] [ O ] [ Br ] [ O ] 2[Na]+ [Na]+ Ca2+ - [Al]3+ 3 [ Cl ] Lewis dot structure examples KBr  AlCl3  CaBr2  Na2O  or or

10. Polyatomics We’ve discussed the formation ionic compounds between two elements, one being + and the other – for ex. NaCl, CaF2, K2O, Al2O3 or AlCl3 These are called binary compounds (two elements) However ionic compounds can also form between Multiple elements for ex. CuSO4 , K3PO4, K2CrO4or NH4NO3 So what’s the difference between these 2 types of ionic compounds? Very pretty!

11. Polyatomics These multi atom ionic compounds are formed With ions known as POLYATOMICS Polyatomic Ions can have either + or – charge They are groups of atoms joined together by covalent bonds that behave as charged ions. Therefore they can form Ionic compounds - example: Na+ + NO3- NaNO3 (We’ll discuss covalent bonds in the next unit)

12. Look at table E in your reference table These are the Common Polyatomic Anions and Cations You need to learn their names & formulas And to recognize Them as polyatomics! To cations add: Dimercury (I) Hg22+ Hydronium ion H3O+

13. Polyatomics Notice there are many more anions(-) than cations (+). Some polyatomics ALSO contain a Metal and nonmetal example: Chromate CrO42-, or Permangenate MnO4- And remember Polyatomics form ionic compounds with metals just like any other binary compound 2K+ + CrO42- K2CrO4 (Potassium Chromate)

14. What are the names of the following polyatomics? 1. OH- 5. CN- 3. ClO- 4. H3O+ 6. NO3- 2. NH4+ What are the formulas of these polyatomics? 1. Nitrite 3. Perchlorate 5. Phosphate 2. Sulfate 4. Hydronium 6. Carbonate

15. Polyatomic Lewis Dot Structures Writing Lewis dot structures for Ionic compounds containing Polyatomic Ions (such as the nitrate ion) in Cu(NO3)2 is a little more complicated This additional complexity arises because polyatomic ions containcovalent bonds We’ll talk about these later after we discuss covalent Bonds.