1. Module 4 Lesson 2 Ionic Naming and Formulas

2. Formulas Chemical formula – Shows kinds and numbers of atoms in smallest representative unit NaCl, H 2 O Formula unit – Ionic compounds form CRYSTALS that vary in size, because the ions attract from all sides, the ions pack together in an alternating pattern, so the formula shows the lowest whole number ratio of ions

3. Oxidation Numbers Oxidation numbers are the charges that an atom takes on to obey the Octet Rule The oxidation number of an element depends on the Group number of the element. Group NumberOxidation Number 1+1 2+2 3-12Usually +2 except Ag and Zn 13+3 14+4 15-3 16-2 17 180

4. Mark your Periodic Table All the transition metals except Ag and Zn can have more than one charge and need a Roman numeral (Pb and Sn need one too!) +1 +2 +1 +2 0 -2 -3 +3 +4

5. Formulas Practice Al + O Be + S Al + Br K + I Mg + I Na + O Sometimes one loses more e- than the other needs, or vice versa, so the ratio cannot be 1:1 look at the charges, criss-cross them so that they become the subscripts, then reduce if possible; the idea is that the overall charge in a chemical formula is ZERO Al +3 O -2  Al 2 O 3 Be +2 S -2  Be 2 S 2  BeS Try the rest of the practice at the top of the page and then check yourself on the following slide 2:2 reduces to 1:1

6. Formulas and Naming Practice Al + O Be + S Al + Br K + I Mg + I Na + O AlBr 3 KI MgI 2 Na 2 O Naming these are easy, you just say the name of the cation and the name of the anion (ending is changed to –ide) Writing these names and formulas is easy because each ion always has the same charge, but this isn’t always the case Aluminum bromide Potassium iodide Magnesium iodide Sodium oxide

7. Naming Ionic Compounds Remember, ionic compounds always have a metal Cations have the same name as the metal (add “ion”) Anions have the ending changed to –ide, or they are polyatomic and have a special name Metals that can form more than one type of ion use a Roman numeral equal to the charge to designate the type Fe +2 is iron(II) Fe +3 is iron(III)

8. Variable Oxidation States As stated on this previous slide, some elements can have more than one oxidation state. This includes many of the Transition Elements as well as Sn and Pb. These require Roman Numerals to show the oxidation state. For example Pb can be +2 or +4 and would thus be represented: Pb (II) and Pb (IV) These Roman Numerals are also required to name these compounds. – For example – PbCl 2 – PbCl 4 Lead (II) chloride Lead (IV) chloride

9. Polyatomic Ions From the …Reference Tables

10. Writing Formulas Polyatomic ion: a group of covalently bonded atoms with an overall charge Criss cross as you did for the other ionic formulas placing the superscript form one as the subscript of the other. K + PO 4 -3 K 3 PO 4 Mg +2 NO 3 - Mg(NO 3 ) 2 Note that you must add parentheses if the number goes for the entire polyatomic ion Try the following: – Ca + hydroxide – K + sulfate – Al + carbonate – Ammonium + O

11. Writing Formulas Ca + Hydroxide Ca +2 OH - Ca(OH) 2 K + Sulfate K + SO 4 -2 K 2 SO 4 Al + carbonate Al +3 CO 3 -2 Al 2 (CO 3 ) 3 Ammonium + O NH 4 + O -2 (NH 4 ) 2 O

12. Naming Polyatomics Naming ionic compounds containing polyatomics is simple! Name as usual except just use the name of the polyatomic ion when it occurs. Example: Ca(OH) 2 Name the cation (Calcium) and then name the polyatomic ion (hydroxide) – Calcium hydroxide – Go to the next slide to see more examples

13. Naming Ionic Compounds Ca + Hydroxide Ca +2 OH - Ca(OH) 2 K + Sulfate K + SO 4 -2 K 2 SO 4 Al + carbonate Al +3 CO 3 -2 Al 2 (CO 3 ) 3 Ammonium + O NH 4 + O -2 (NH 4 ) 2 O Calcium hydroxide Potassium sulfate Aluminum carbonate Ammonium oxide