Rules For Writing Chemical Formulas and Naming Compounds-Ionic

Binary Ionic Compounds Binary compound - made of two elements Oxidation number – tells you how many electrons an atom loses or gains to form an ionic compound; positive or negative; (become stable) Some metals can have more than one oxidation number

CaCl2 = calcium chloride Naming Binary Ionic Compounds: 1. Cation first, then anion 2. Cation = name of the element Ca2+ = calcium ion 3. Anion = root + -ide Cl- = chloride CaCl2 = calcium chloride

Naming Binary Ionic Compounds Examples: NaCl ZnI2 Al2O3 sodium chloride zinc iodide aluminum oxide

Learning Check Complete the names of the following binary compounds: Na3N _____________ KBr _____________ Al2O3 _____________ MgS _____________

Learning Check Complete the names of the following binary compounds: Na3N _Sodium Nitride____________ KBr _Potassium Bromide_______ Al2O3 _Aluminium Oxide______ MgS _Magnesium Sulfide_______

Transition Metals Elements that can have more than one possible charge MUST have a Roman Numeral to indicate the charge on the individual ion.

1+ or 2+ 2+ or 3+ Cu+, Cu2+ Fe2+, Fe3+ copper(I) ion iron(II) ion copper (II) ion iron(III) ion

Examples FeCl3 (Fe3+) iron (III) chloride CuCl (Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide

Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr2 +2 iron (_____) bromide CuCl +1 copper (_____) chloride SnO2 +2 ___(_____ ) ______________ Fe2O3 +3 ________________________ Hg2S +1 ________________________

Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr2 +2 iron (__II___) bromide CuCl +1 copper (__I___) chloride SnO2 +2 _Tin__(__II___ ) _Oxide___ Fe2O3 +3 _Iron (III) Oxide_____ Hg2S +1 __Mercury (I) Sulfide______

Writing Formulas 1.Write the symbol of the element or polyatomic ion (ions containing more than one atom) that has the positive oxidation number. Hydrogen and ammonium (NH4) and all metals are positive.

Writing Formulas 2. Write the symbol of the element or polyatomic ion with the negative oxidation number. Nonmetals other than hydrogen and polyatomic ions other than NH4 are positive. 3. Use subscripts next to each ion so that the total charge of all ions is zero.

Short-cut method: CrissCross This method ‘criss-crosses’ the ion charges to the subscript position IF you use criss-cross, be careful to simplify the formula keeping whole numbers! ex. Na+ (sodium ion) and Cl- (chloride ion) Na+ Cl- Na1Cl1 NaCl ex. Ca2+ (calcium ion) and O2- (oxide ion) Ca2+ O2- Ca2O2 CaO (divide both by two to simplify) 1 1

Rules for using oxidation numbers to create compounds Positive ions can only bond with negative ions and vice versa 2. The sum of the oxidation numbers of the atoms in a compound must be zero (the key is to stay balanced) 3. If the oxidation numbers are not equal to zero, then you must add additional elements until they balance at zero. 4. When writing a formula the symbol of the Positive (+) element is followed by the symbol of the negative (-) element.

Compounds are neutral For every positive, there must be a negative Group 1 is + 1 Group 2 is +2 Group 13 is +3 Group 14 is +4 Group 15 is -3 Group 16 is -2 Group 17 is -1 Group 18 is 0

Learning Check What is the correct formula for the compounds containing the following ions: 1. Na+, S2- a) NaS b) Na2S c) NaS2 2. Al3+, Cl- a) AlCl3 b) AlCl c) Al3Cl 3. Mg2+, N3- a) MgN b) Mg2N3 c) Mg3N2

Solution 1. Na+, S2- b) Na2S 2. Al3+, Cl- a) AlCl3 3. Mg2+, N3- c) Mg3N2

Polyatomic Ions NO3- nitrate ion NO2- nitrite ion

Polyatomic Compounds   Some compounds like calcium carbonate and copper (II) sulphate do not end in “ide” like other ionic compounds. Why? Such compounds are pure substances that involve a metal ion and a polyatomic or complex ion. Polyatomic ions are groups of atoms that tend to stay together and carry an overall charge. E.g. sulphate ion is SO4 -2 Free Template from www.brainybetty.com

Free Template from www.brainybetty.com

DO NOT have to write but take a look!

Writing Formulas for Polyatomic Compounds   What is the formula for copper (II) sulphate 1)      write the symbols for the metal and the polyatomic group Cu SO4 Free Template from www.brainybetty.com

2) write the ionic charges +2 -2 Cu SO4 +2 -2 Cu SO4 Free Template from www.brainybetty.com

  3)   Criss Cross and reduce the subscripts to their simplest terms if possible. (Brackets) may be needed if there is 2 or more polyatomic ions. Never change the subscript of the polyatomic group. Cu2 SO42 = Cu2 (SO4)2 = Cu SO4 Free Template from www.brainybetty.com

Naming Polyatomic Compounds   The name of the above compound is Copper (II) Sulphate The name is simply the name of the metal (use a roman numeral if the metal has more than 1 positive charge) and the name of the polyatomic ion . Both can be found on the periodic table by looking them up. Free Template from www.brainybetty.com

Writing Formulas: Polyatomic Write each ion, cation first. Don’t show charges in the final formula. Overall charge must equal zero. If charges cancel, just write symbols. If not, use subscripts to balance charges. Use parentheses to show more than one of a particular polyatomic ion. Use Roman numerals indicate the ion’s charge when needed

Examples Sodium Sulfate Na+ and SO4 -2 Na2SO4 Iron (III) hydroxide Fe+3 and OH- Fe(OH)3 Ammonium carbonate NH4+ and CO3 –2 (NH4)2CO3

Learning Check 1. Aluminum (III) nitrate a) AlNO3 b) Al(NO)3 c) Al(NO3)3 2. copper(II) nitrate a) CuNO3 b) Cu(NO3)2 c)Cu2(NO3) 3. Iron (III) hydroxide a) FeOH b) Fe3OH c) Fe(OH)3 4. Tin(IV) hydroxide a) Sn(OH)4 b) Sn(OH)2 c)Sn4(OH)

Learning Check Match each set with the correct name: 1. Na2CO3 a) magnesium sulfite MgSO3 b) magnesium sulfate MgSO4 c) sodium carbonate 2 . Ca(HCO3)2 a) calcium carbonate CaCO3 b) calcium phosphate Ca3(PO4)2 c) calcium bicarbonate

Mixed Practice! Name the following: Na2O CaCO3 PbS2 Sn3N2 Cu3PO4 HgF2

Mixed Up… The Other Way Write the formula: Calcium nitride Aluminum (III) carbonate Potassium bromide Barium fluoride Cesium hydroxide