2 Today you will need your periodic table/ion sheet and your packet Warmup (3 minutes) What is a valence electron?Draw the Lewis dot structures of magnesium and fluorine.What does the term “neutral” mean (in terms of math and science)?
3 Is the red guy a cation or an anion? Is the red guy a metal or a nonmetal?Chemistry puts the "cation" in education. What's a cation afraid of?A dogion!
4 Ion: An atom (or group of atoms) that has lost or gained e- to follow the Octet Rule and is now electrically chargedMetal atoms lose e- to form positive ions called cations:K+Ca 2+NH4+Nonmetal atoms gain e- to form negative ions called anions:Cl-S2-CO32-Superscript written to the upper right shows the chargeIf the charge is +1 or -1, you don’t have to include the “1”Called an “oxidation number”Mg2+F-
5 Write the (reduction) equation showing how flourine becomes an ion IonizationF + e- F-Neutral but unstable fluorine atom, FSame # electrons as neon, but NOT an atom of neon!Write the (oxidation) equation showing how magnesium becomes an ionMg Mg2+ + 2e- Same # e- as…which element?
6 What patterns do you see? Are there any exceptions to these patterns? 1A metals: +1 ions 2A metals: +2 ions7A nonmetals: -1 ions 6A nonmetals: -2 ions
7 Special ions (refer to handout) Some transition metals lose different numbers of electrons when they become ionsThey can have different charges as a cation, and must be written with roman numerals representing their charge (exception: Al3+)Examples?Polyatomic ions: group of more than one atoms with a charge (+ or -)Example: Why do chemists like nitrates so much?They're cheaper than day rates.
8 Ionic Bonds Na+ Cl- Nonmetal atoms remove e- from metal atoms. The two atoms become oppositely charged ions that attract each other, resulting in an ionic bond. An ionic compound forms.Cl-Read through EX 1 on “Writing and Naming Ionic Compounds” Handout that shows the crisscross method.
9 another example: iron(II)phosphate Fe2+ PO43- Fe2(PO4)3 NOOOOOOO! EX 2: Write the formula for the ionic compound calcium oxide Step 1: Write each ion with the correct charge. Look at periodic table group or cheat sheet for help. Ca2+ O2- Step 2: “Criss-cross” number associated with each charge (do not include the + or -) Ca2O2 Step 3: Remove any subscripts of 1. Eliminate both subscripts if they are the same. Write the formula. CaOEX 3: Write the formula for the ionic compound aluminum carbonateAl3+ CO32-Al2CO33 ????Al2(CO3)3another example: iron(II)phosphateFe2+ PO43-Fe2(PO4)3 NOOOOOOO!Fe3(PO4)2
10 PO43-Fe 2+Fe 2+PO43-Fe 2+6-6+Ionic compounds aren’t present as individual molecules, they exist as large crystals with many many of the same ions. The subscripts show the RATIOS of the two ions --- one formula unit of this compound has 3 iron(II)’s and 2 phosphates.Fe 2+Fe 2+Fe 2+PO43-PO43-PO43-PO43-3:2 is simplified from 6:4or 30,000:20,000Fe 2+Fe 2+Fe 2+
11 Name Formula potassium nitride copper (I) bromide potassium phosphidemagnesium fluorideK3NCuBrK3PMgF2
12 Name these 2 compounds:CoSFigure out which ions form the compound because the ion charge could be important.Since S forms S2-, Co must be Co2+b. Name the ions, cation first, then anionc. Change ending to –ide if it’s a pure element.cobalt (II)sulfided. Transition metals always get a roman numeral to indicate their charge!Na2SO3sodium sulfiteCommon mistakes:sodium(II)sulfitesodium(I)sulfitesodium sulfide/sulfate
13 Formula Name Na2O CuS LiBr CuCl Sodium Oxide Copper (II) Sulfide Lithium BromideCopper (I) Chloride
14 Name Formula Ammonium Phosphate Iron (II) Nitrate Sodium Sulfate Silver Acetate(NH4)3PO4Fe(NO3)2Na2SO4AgC2H3O2
15 Formula Name Fe(OH)3 Mg(NO2)2 NiCO3 Cd(HCO3)2 Iron (III) Hydroxide Magnesium NitriteNickel (II) CarbonateCadmium (II) hydrogen carbonateorCadmium (II) bicarbonate
16 Name Formula Sodium Dichromate Tin (II) Chromate Magnesium Permanganatelead (IV) bisulfateNa2Cr2O7SnCrO4Mg(MnO4)2Pb(HSO4)4
17 Work on your packet! Make sure you have the Precipitation Lab with you next class!