Wri$ng and Naming Chemical Compounds Ionic Compounds Review: Common Oxidation Numbers (Charges) +1 +2 +3 ±4 -3 -2 Cation- Positive ion that has LOST electrons (Metals) Anion- Negative Ion that has GAINED electrons (Nonmetals) -1 0 Polyatomic Ions you MUST know: Nitrate NO3-‐ Carbonate CO3-‐2 Sulfate SO4-‐2 Phosphate PO4-‐3 Hydroxide OH-‐ Acetate C2H3O2-‐ (CH3COO-‐) Ammonium NH4+ •  Remember polyatomic ions STAY TOGETHER!!!! Bonding Review: •  Ionic compounds are formed when a metal transfers electrons to a nonmetal –  Ca$on (metal) + Anion (nonmetal) = Ionic bond –  Ca$on (metal) + Polyatomic Ion = Ionic bond –  Polyatomic ion + Anion (nonmetal) = Ionic bond –  Polyatomic Ion + Polyatomic Ion = Ionic bond Wri$ng Formulas for Ionic Compounds •  Rules: –  The symbol tells the element and the subscript (liVle number to the right of the symbol) tells how many of each element is in the formula –  The ca$on (metal ion) or posi$vely charged polyatomic ion is always wriVen ﬁrst and the anion (nonmetal ion) or nega$vely charged polyatomic ion is always wriVen second Wri$ng Formulas for Ionic Compounds 1) Start by wri$ng the ca$on and anion separately with their charges Ex: If you want to write the chemical formula for magnesium and chlorine Mg+2 and Cl-‐1 2) Criss-‐cross the charges so that they become the subscripts but drop the +/-‐ signs Ex: The +2 charge from Mg will become the 2 subscript for Cl and the -‐1 charge from Cl will become the 1 subscript for Mg Mg1Cl2 (You don’t have to write the 1 so the formula correctly wriVen would be MgCl2) 3) Reduce the subscripts if they can be reduced. In this case, they can’t, so you are done!!! Now You Try! •  •  •  •  •  •  •  1) lithium and ﬂuorine 2) calcium and sulfur 3) cesium and oxygen 4) aluminum and oxygen 5) sodium and sulfur 6) aluminum and chlorine 7) potassium and oxygen Check Your Answers: •  •  •  •  •  •  •  1) LiF 2) CaS 3) Cs2O 4) Al2O3 5) Na2S 6) AlCl3 7) K2O Wri$ng Ionic Formulas for Compounds with Polyatomic Ions 1)  Start by wri$ng your anion and ca$on with their charges separately –  –  If your anion or ca$on is a polyatomic ion, place parenthesis around it and put the charge on the outside of the parenthesis Ex: If you are wri$ng the formula for sodium and carbonate: Na +1 and (CO )-‐2 3 2) Criss-‐cross the charges so that they become the subscripts but drop the +/-‐ signs –  –  Place the subscript on the outside of the parenthesis of your polyatomic ion. MAKE SURE NOT TO SEPARATE WHAT WAS INSIDE THE PARENTHESIS!!! Ex: Na2(CO3) Now You Try! •  •  •  •  •  1) aluminum and nitrate 2) magnesium and phosphate 3) ammonium and chlorine 4) calcium and acetate 5) sodium and hydroxide Check Your Answers: •  •  •  •  •  Al(NO3)3 Mg3(PO4)2 (NH4)Cl Ca(C2H3O2)2 Na(OH) Oxida$on Number Excep$ons •  Since the oxida$on numbers of transi$on metals cannot be predicted by looking at the group numbers, you will need to memorize the oxida$on numbers for these excep$ons –  Ag+1 –  Zn+2 –  Cd+2 –  Hg2+2 mercury (I) –  Hg+2 mercury (II) These Roman Numerals will make since in about 3 slides Naming Binary Ionic Compounds •  Binary means there are only two elements in the compound •  Rules for Naming: –  1) Name the metal –  2) Shorten the name of the non-‐metal and add the suﬃx “– ide” –  Ex: KCl would be named potassium chloride Now You Try! •  Name the following compounds: –  1) MgBr2 –  2) NaF –  3) Al2O3 –  4) CdO –  5) ZnS –  6) Na2O –  7) K3N Check Your Answers: •  •  •  •  •  •  •  1) magnesium bromide 2) sodium ﬂuoride 3) aluminum oxide 4) cadmium oxide 5) zinc sulﬁde 6) sodium oxide 7) potassium nitride Naming Ionic Compounds with Transi$on metals •  Since the oxida$on numbers of transi$on metals cannot be predicted by looking at the group numbers, a roman numeral must be used to name the oxida$on state of the transi$on metal in a compound –  Transi$on metals can have more than one oxida$on number (charge) •  The only excep$on to this rule is when naming the transi$on metals you were told to memorize (silver, zinc, cadmium, mercury s$ll needs a roman numeral) •  To ﬁnd the roman numeral, you must WORK BACKWARDS and uncriss-‐ cross your charges! –  Ex: FeCl2 uncriss-‐crossed is Fe+2 and Cl-‐, so the Roman numeral when naming iron is (II) therefore the name of the compound is iron (II) chloride Now You Try! •  •  •  •  •  1) SnO 2) CuS 3) Hg2I2 4) CuI 5) PbO2 Check Your Answers: •  •  •  •  •  1) $n (II) oxide 2) copper (II) sulﬁde 3) mercury (I) iodide 4) copper (I) iodide 5) lead (IV) oxide So how do you write the formula for a compound with a transi$on metal? •  Same process as naming ionic compounds only the Roman numeral is the oxida$on number, so use it as the charge! –  Iron (III) oxide •  EX: Fe+3 and O-‐2 is wriVen Fe2O3 Now You Try! •  Write the formula for the following compounds: –  1) Tin (IV) chloride –  2) Lead (IV) oxide –  3) Tin (II) sulﬁde –  4) Mercury (II) bromide –  5) Mercury (I) ﬂuoride –  6) Copper (II) nitride –  7) Iron (II) iodide Check Your Answers: •  •  •  •  •  •  •  1) SnCl4 2) PbO2 3) SnS 4) HgBr2 5) Hg2F 6) Cu3N2 7) FeI2 Naming Ionic Compounds with Polyatomic Ions •  Rules for naming: 1) Name the metal or posi$vely charge polyatomic ion ﬁrst 2) If the anion is a polyatomic ion, just name the polyatomic ion as is. If the anion is a non-‐metal replace the ending with –ide just like you would if you had a regular binary compound •  If you have two polyatomic ions, name the posi$vely charged poly ﬁrst followed by the nega$vely charged poly –  Ex: Al(NO3)3 would be named aluminum nitrate –  Ex: (NH4)Cl would be named ammonium chloride –  Ex: (NH4)(NO3) would be named ammonium nitrate Molecular Compounds Review: •  Molecular compounds are formed when two nonmetals form a covalent bond •  These compounds are called molecules –  Covalent bonds are the result of atoms sharing electrons –  Nonmetal + nonmetal = molecule Naming Molecular Compunds •  We use Greek Preﬁxes to indicate the number of atoms of each element that are present –  –  –  –  –  –  –  –  –  –  1-‐ mono (not used if for the ﬁrst element) 2-‐ di 3-‐ tri 4-‐ tetra 5-‐ penta 6-‐ hexa 7-‐ hepta 8-‐ octa 9-‐ nona 10-‐ deca Naming Molecular Compounds •  Rules for naming: –  1) Name the ﬁrst element using the appropriate preﬁx that indicates how many atoms are present •  If there is only 1 element present you do not name it using mono –  2) Name the second element using the appropriate preﬁx and change the ending to –ide –  EX: CO would be named carbon monoxide –  EX: Cl2O7 would be named dichlorine heptoxide Now You Try! •  •  •  •  •  1) CO2 2) N2O3 3) Cl2O 4) SO3 5) P4O10 Check Your Answers: •  •  •  •  •  1) carbon dioxide 2) dinitrogen trioxide 3) dichlorine monoxide 4) sulfur trioxide 5) tetraphosphorus decoxide Diatomic Elements •  There are 7 elements that can’t exist as single atoms in nature so they must be wriVen as two atoms when they are not combined into compounds •  They are just called by their elemental names •  You must MEMORIZE these: –  –  –  –  –  –  –  Hydrogen, H2 Oxygen, O2 Nitrogen, N2 Fluorine, F2 Chlorine, Cl2 Bromine, Br2 Iodine, I2 You can remember these: Mr. and Mrs. BrINClHOF