H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C Chemical Formula Like a word Lists what elements are present in the compound Describes Compounds Subscripts = how many atoms of element to left of #. Expresses the ratio of each element present

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Chemical Formula cont.. Example: CaI 2 The small 2 is a subscript. It indicates that for each molecule of calcium iodide, 1 atom of calcium is present for each 2 atoms of iodine.

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Chemical Formula Practice Consider the formula for potassium nitrate (KNO 3 ): How many atoms of nitrogen are present? How many atoms of oxygen are present? 3 How many atoms of potassium are present? 1 1

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Your Turn….. CaCl 2 KCl MgBr 2 Na 2 S Sr 3 N 2 How many atoms of each element are in each of the formulas below? Pb 2 (CrO 4 ) 3 NH 4 NO 2 Mg(NO 3 ) 2 (NH 4 ) 2 S Ca(NO 3 ) 2

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Remember…….Ionic Compounds Composed of (+) cation and (-) anion for a net charge of zero These charges are also called “oxidation numbers”

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Charges? Cations: Group 1 A = +1 Group 2A = +2 Group 3A (metals (below the zig-zag line)) = +3 Group 4A (metals (below the zig-zag line)) = +4 Group 5A (metals (below the zig-zag line))= +5 Group 6A (metal (below the zig-zag line)) = +6

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Charges? Cont… Anions: Group 8A = 0 (noble gases) Group 7A = -1 Group 6A = -2 Group 5A (non metals (above the zig-zag line)) = -3 Group 4A (non metals (below the zig-zag line)) = -4 Group 3A (non metals (below the zig-zag line)) = -5

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 IONIC Bonds in IONIC compounds! What does ION mean? Charged particles Remember our example…NaCl. + - ZERO How do atoms become charged? gain or give away ELECTRONS The whole compound has to equal

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 How do I write Ionic Compound Formulas ? 1.Write each element’s symbol with its charge = ion formula 2.Place the Cation (+) ion first and then place the anion (-) second. 3.Move the superscript (charge of the first ion) to the bottom (subscript) of the second ion.

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 How do I write Ionic Compound Formulas ? 4. Make the subscripts positive (+). Note: If the subscript is 1 then no subscript is needed. Double check: The charges X the # of ions on each ion should add up to a net charge of zero.

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Lets Practice… Cation Anion Formula Na + O -2 = Na 2 O Write the formula for Sodium Oxide Na 2 O = 2 atoms of Na + & 1 atom of O -2 Na + + Na + + O -2 = 0 (+1) + (+1) + (-2) = 0

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 This is called the “criss-cross” method Cation Anion Formula Ca +2 Cl -1 = CaCl 2 Al +3 Cl -1 = AlCl 3 Li +1 N -3 = Li 3 N Mg +2 N -3 = Mg 3 N 2 Calcium chloride Aluminum chloride Lithium nitride Magnesium nitride

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Your Turn…..Write the Formula for aluminum sulfide Cation Anion Formula Al +3 S -2 = Al +3 + Al +3 + S -2 + S -2 + S -2 = 0 Al 2 S = 0 Al 2 S 3 = 2 atoms of Al +3 & 3 atom of S -2

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 What about transitional elements? 1.If given the name, the charge is provided with a Roman numeral 2.If given the formula, write the charge in Roman numerals in parenthesis iron (II) oxide = Fe +2 and O -2 = FeO copper (I) oxide = Cu +1 and O -2 = Cu 2 O Pb 2 O 4 = Pb +4 and O -2 = lead (IV) oxide

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Transitional elements are easy… cobalt (III) chloride gold (I) sulfide lead (II) iodide iron (III) oxide chromium (II) sulfide copper (II) chloride lead (IV) iodide CoCl 3 Au 2 S PbI 2 Fe 2 O 3 CrS CuCl 2 PbI 4

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Name these transitional elements manganese (IV) oxide chromium (III) oxide lead (II) chloride iron (III) iodide chromium (III) sulfide copper (I) chloride platinum (IV) iodide Mn 2 O 4 Cr 2 O 3 PbCl 2 FeI 3 Cr 2 S 3 CuCl PtI 4

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Polyatomic Ions Group of bonded atoms w/a charge Place polyatomic ion in ( ) and treat as one unit and place the subscript on the outside of the (). If the polyatomic is taken only once then () are not needed. Ex: (PO 4 ) 3- Phosphate ion with 3- charge

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Common Polyatomic ions + 1 charge NH 4 + Ammonium OH - Hydroxide CO 3 -2 Carbonate PO 4 -3 Phosphate NO 3 - Nitrate SO 4 -2 Sulfate NO 2 - Nitrite SO 3 -2 Sulfite

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Lets Practice… Formula for potassium carbonate Cation Anion Formula K + (CO 3 ) -2 = remove parentheses K 2 CO 3 K + K + (CO 3 ) -2 =0 K 2 (CO 3 )

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Formula for zinc nitrate Cation Anion Formula Zn +2 (NO 3 ) -1 = Zn(NO 3 ) 2 Zn +2 (NO 3 ) -1 (NO 3 ) -1 = 0

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 What about Ionic Formulas with Polyatomics? NH 4 & Cl Al & NO 3 Ca & CO 3 K & PO 4 (NH 4 ) 2 Cl ammonium chloride Al(NO 3 ) 3 aluminum nitrate CaCO 3 calcium carbonate K 2 PO 4 potassium phosphate

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 Let’s put it all together… sodium hydroxide mercury (II) sulfate lead (IV) phosphate ammonium sulfide aluminum chlorate copper (I) carbonate manganese (IV) oxide aluminum nitrate iron (II) phosphate sodium chromate ammonium chromate NaOH HgSO 4 Pb 3 (PO 4 ) 4 (NH 4 ) 2 S Al(ClO 3 ) 3 Cu 2 CO 3 Mn 2 O 4 Al 2 (NO 3 ) 3 FePO 4 Na 2 CrO 4 (NH 4 ) 2 CrO 4

H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C H2CH2C CH 2 How about the other way? calcium hydroxide lead (II) sulfate copper (II) phosphate ammonium oxide aluminum bromate copper (II) carbonate manganese (IV) sulfide aluminum sulfate iron (III) phosphate lithium chromate ammonium carbonate Ca(OH) 2 PbSO 4 Cu 3 (PO 4 ) 2 (NH 4 ) 2 O Al(BrO 3 ) 3 CuCO 3 Mn 2 S 4 Al 2 (SO 4 ) 3 Fe 2 (PO 4 ) 3 Li 2 CrO 4 (NH 4 ) 2 CO 3