1. Lesson 23 Ions & Ionic Compound Formation
Objectives:
-         The student will explain what is involved in creating an ion.
-         The student will name ionic compounds
-         The student will write formulas for ionic compounds.
PA Science and Technology Standards: A; A

3. I. Ions. a. Ionic Compound – a compound in which the elements
I. Ions a.       Ionic Compound – a compound in which the elements which make it up are held together by the attraction of opposite charges.                          i.      These charges are created by elements giving up or picking up electrons to get 8 in their outer level. 1.      Each electron left creates a +1 charge. 2.      Each electron gained creates a –1 charge.                          ii.      The difference in charges creates an attraction between/among the elements in the compound, forming an ionic bond.                          iii.      All ions are either positively or negatively charged. 1.      Cation – a positively charged ion 2.      Anion – a negatively charged ion                          iv.      An ion can be composed of a single element, or a group of elements acting together. 1.      Monatomic ion – an ion composed of a single atom. 2.      Polyatomic ion - an ion made of two or more atoms bonded together that function as a single ion.

4. v. Writing and Naming ions. 1
              v.      Writing and Naming ions 1.      To write the symbol for a monatomic ion, write the symbol, followed by a superscript indicating the charge. The sign for the charge always follows the number if it is more than       The system for naming chemical substances is known as nomenclature. 3.      Monatomic cations are named by using the name of the original element, and following it by the word ion. Ex – Sodium ion 4.      Monatomic anions are named by dropping the end of the element’s name and adding the suffix –ide, and then adding the word ion. Ex – Chloride ion 5.      Polyatomic ions have specific names associated with them; you either have to know them or find them on a list Examples: Mg2+ (magnesium ion) N3- (nitride ion)  

5. Polyatomic Ions
  (THIS IS ON PAGE 425 OF YOUR LECTURE NOTES: APPENDIX 4)
 1+ Ions Ions
ammonium, NH4+1 mercury I, Hg2+2
1-  Ions      Ions    3-  Ions
acetate, CH3COO-, C2H3O2- carbonate, CO32- arsenate, AsO43-
amide, NH2- chromate, CrO42- citrate, C6H5O73-
azide, N3- dichromate, Cr2O72- hexacyanoferrate III, Fe(CN)63-
benzoate, C6H5COOH hexachloroplantinate IV, PtCl62- phosphate, PO43-
bicarbonate, HCO3- hexafluorosilicate, SiF62-
bisulfate, HSO4- molybdate, MoO42-
bromate, BrO oxalate, C2O42-
chlorate, ClO3- peroxide, O22-
cyanide, CN- peroxydisulfate, S2O82-
formate, HCOO- selenate, SeO42-
hydroxide, OH- silicate, SiO   Ions   
hypochlorite, ClO- sulfate, SO42-
hypophosphite, H2PO2- sulfite, SO32- hexacyanoferrate II, Fe(CN)64-
iodate, IO3- tartrate, C4H4O62- diphosphate, P2O74-
metaphosphate, PO3- tellurate, TeO42-
nitrate, NO3- tetraborate, B4O72-
nitrite, NO2- thiosulfate, S2O32-
perchlorate, ClO4- tungstate, WO42-
periodate, IO4-
permanganate, MnO4-
peroxyborate, BO3-
thiocyanate, SCN-
vanadate, VO  

6. b. The octet rule cannot always predict changes. i
b.      The octet rule cannot always predict changes    i.      Some ions do not follow the octet rule.               ii.      Many transition metals can achieve a stable arrangement without having a full octet.           iii.      Many transition metals also have the ability to become stable in more than one way.               iv.      You need to refer to a table which has ions with more than one charge listed to determine what possibilities exist.

7. c. Nomenclature for ions that can have other charges. i
c.      Nomenclature for ions that can have other charges    i.      Chemists use a system involving roman numerals to indicate charge.    ii.      Example – copper can form a 1+ or a 2+ ion. 1.      Cu+ is called a copper I ion       Cu2+ is called a copper II ion       iii.      Roman numerals are not used for ions that always form the same charge.       iv.      An older system uses the suffixes –ous to indicate the lower charge, and the suffix –ic to indicate the higher charge, when there are two common charges       Cuprous or Copper (I) and Cupric or Copper (II) 2.      Ferrous or Iron (II) and Ferric or Iron (III)

8. v. Examples:. Lead (IV). Iron (III). Copper (II)
    v.      Examples: Lead (IV) Iron (III) Copper (II) Silver (I) The roman numeral refers to the oxidation number of the metal ion. Remember that these are always positive numbers with the metals, since metals lose electrons. The majority of the time we see this occur, we will be dealing with a transition metal. If you are given a transition metal and no special charge is indicated than assume the oxidation number is positive 2
                                                              

9. II. Naming ionic compounds. a. Binary compounds. i
 II. Naming ionic compounds a. Binary compounds  i. Binary compound: compound composed of just two elements. ii.      To name the compound, just combine the names of the two ions.                    iii.      Examples 1.      Sodium and chlorine – sodium chloride 2.      Barium and oxygen – barium oxide                      iv.      Remember that the total charge of a compound must be equal to zero – you may need to have more of the cation or anion in order to balance the charges                           v.      Notice that sodium is 1+, and chlorine is 1-. Also, barium is 2+, and oxygen is 2-. Everything balances when they are combined 1:1.

10. vi. Examples:. CaS. Calcium sulfide. K20. Potassium oxide. Li3P
 vi.  Examples: CaS Calcium sulfide K20 Potassium oxide Li3P Lithium phosphide HI Hydrogen iodide

11. b. Naming ionic compounds involving polyatomic ions. i
b.      Naming ionic compounds involving polyatomic ions.    i.      Same rules will apply as with binary compounds.               ii.     Place the names of the positive ion in front of the name of the negative ion.               iii.    Example: (NH4)3N Ammonium nitride Mg3(PO4)2 Magnesium phosphate

12. c. Naming Binary compounds that involve transition metals. i
c.      Naming Binary compounds that involve transition metals.   i.      Transition metal we have seen have varying charges.                              ii.     The charge of the metal must be indicated in the name of the ionic compound through the use of roman numerals and parenthesis.                        iii.    Examples: CuCl2 Copper (II) chloride FeN Iron (III) Nitride

13. d. Acids. i. Many acids have a common name instead of using their
d.      Acids    i.      Many acids have a common name instead of using their systematic name. These should be memorized – they should become more familiar with use, but you are responsible for knowing all of them       Hydrogen Acetate – Acetic acid 2.      Hydrogen Chloride – Hydrochloric acid 3.      Hydrogen Iodide – Hydroiodic acid 4.      Hydrogen Bromide – Hydrobromic acid 5.      Hydrogen Sulfate – Sulfuric acid 6.      Hydrogen Sulfite – Sulfurous acid 7.      Hydrogen Phosphate – Phosphoric acid 8.      Hydrogen Nitrate – Nitric acid 9.      Hydrogen Nitrite – Nitrous acid 10.  There are other possibilities, but these cover the ones most often encountered.

14. III. Writing formulas for ionic compounds. a
III. Writing formulas for ionic compounds   a.      Ionic compounds have balanced charges.                   i.      Since the charges must equal zero in a neutral compound (any we will be working with will be neutral), you can determine the subscripts for the elements in the formula based on their charges.         ii.     Remember that you can get this information from the periodic table      iii.    Examples 1.      Manganese (IV) and oxygen – Mn4+ and O2-, so therefore, you need two O’s to balance the one Mn, or MnO       Aluminum and oxygen – Al3+ and O2-, so therefore, you need three O’s to balance two Al’s (there is no lower ratio than 2:3 Al:O), or Al2O3.

15. More Examples: Common Pitfalls Many students become confused when doing this step. A simple method for determining subscripts for binary compounds is to criss-cross the numbers. The charge on the first element becomes the subscript on the second, and vice versa. No + or - signs remain – just drop them.   Example Na + O – Mg+2 P … becomes Na2O Mg3P2 This makes writing formulas fast, just remember that the positive ion (metal) always comes first, and reduce to the lowest common whole number ratio.

16. Examples to try: Strontium and Fluorine Lithium and Chlorine
Beryllium and Oxygen
Ammonium and Bromine
Copper (II) and Iodine
6. Lead (IV) and Phosphate

17. v. Chemical formulas must reflect actual composition of. compounds. 1
v.      Chemical formulas must reflect actual composition of compounds 1.      The formulas must represent possible structures       NaCl forms instead of something like Na2Cl because forming a Na2+ removes the second electron from a stable octet, therefore making the ion less stable Nature normally doesn’t allow this       If the process allowed for more energy to be released later because of Na2+, it would be more likely to occur in nature.

18. vi. Ionic formulas show the smallest ratio of ions. 1
                    vi.      Ionic formulas show the smallest ratio of ions 1.      It would be incorrect to write Ca2F4, or Na2Cl2, because of one of the rules of writing ionic formulas       All ionic formulas need to be expressed in the lowest whole-number ratio of the atoms that form the compound       Without following this rule, it would be possible to write thousands of correct formulas for any particular ionic compound. This keeps everyone on the same page.  

19. Questions:
1. Describe what must occur for an ion to form, and the effect of each of the two possibilities.
2. When naming cations which have more than one possible charge, describe the two systems that can be used to identify the charge on the ion.
3. Describe the difference between monatomic and polyatomic ions.
4. What element do all acids contain?