Post on 22-Feb-2016
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Unit3 – Lecture 8
Recap – Bonding Occurs……to fill the outer level of electrons of
elementsyou can predict bonding by observing
trends on the periodic table: type of element: metals, non metals, etc
valence electrons: for lewis diagrams
oxidation #: criss-cross method
Counting AtomsChemical Formula -
shows how many of which atoms are in a molecule
Coefficient - placed in front of a molecule to show more than one molecule
Subscript - number placed below and behind a symbol to show how many of which atoms are present
3H2O
Counting AtomsDiatomic Molecule -
two atoms of the same nonmetal (usually in gas form) that have bonded together
Reactive nonmetals will bond with one another if no other substance is available for bonding
H2 N2
O2 F2
I2 Cl2
Br2
Polyatomic Ionsa group of atoms that
behave as one atomkeep together as a unitif more than one
polyatomic ion is present in a molecule, parentheses set it apartStill use a subscript to
show how manyHow many (OH)?
Ca(OH)2
NH4Cl
Common Polyatomic IonsSee your packet…
How Many?Making formulae –
the “Criss Cross” Method background:uses oxidation numbers to predict # of each
element in a compound when 2 elements bondOxidation # Review:
+ or – sign, indicates # of electrons that will be gained or lost
written like a charge in the upper right always included [given to you] if you have
polyatomic ions
Oxidation/Charge Numbers +1 +2 ----------------------------------------- +3 +/-4 -3 -2 -1 0
Oxidation #s – cont’dTransition metals have more than one
oxidation number!!!!Fe[III] = Fe+3 = Iron with +3 oxidation numberFe[II] = Fe+2 = Iron with +2 oxidation numberMn[II] = Mn+2 = Manganese with +2 oxidation
numberMn[III] = Mn+3 = Manganese with +3
oxidation number
Making Formulae – the “Criss-Cross” Methodcation first – write element & oxidation #anion next – write element & oxidation #without the + or – sign
write the oxidation # from one symbolon the other as a subscript
remember to add parentheses aroundpolyatomic ions
don’t write the #1, it is impliedreduce any evenly-divisible subscripts
ExamplesBond btw Aluminum and Oxygen
Bond btw Aluminum and Carbonate [CO3]-2
ExamplesBond btw Aluminum and OxygenAl +3 O -2
Al2O3
Bond btw Magnesium and Borate[BO3]-3
Mg +2 (BO3) -3
Al3(BO3)2
Practice Complete practice problems 1-9 in your packet.
Reverse Criss-Crossuse to find oxidation on atoms in a compound.
PCl3 P Cl3 So… P is 3, and Cl is 1
for transition metals – VERY useful
Ti Cl2 Ti Cl2 So… Ti is 2 and Cl is 1
Oxidation for Ti is +2
Binomial Nomenclaturea “two name” “naming” system
like Genus species from biology….Used to differentiate between elements and
compoundsFluorine (an element) vs
Fluoride (part of a compound)Never change the name of a Polyatomic Ion
Big difference between Sulfide, Sulfite, and Sulfate
Naming Ionic CompoundsList the positive ion (or metal) first
***Use Roman Numerals to show the Oxidation number of a transition metal
Name the negative ion (or nonmetal), changing the ending to –ide“Oxide”“Sulfide”“Phosphide”
Ex: FeO / Fe2O3
= Iron II Oxide / Iron III Oxide
Practice Complete practice – Naming Ionic Cmpds
page 14
Naming Polyatomic Compoundscmpd is polyatomic if there are more than 2
elements You will be given the names for common polyatomics.
Still only 2 words in the namefirst term = positive ion name second term = negative ion name
if second term is NOT a polyatomic, change ending to -ide
if the second term is a negative polyatomic, do NOT change the ending
Practicecomplete the practice problems 1-3.
Homeworkfinish any practice problems from lecture
complete Naming IONIC Compounds w/s [1-14] ONLY
HONORS ONLY:make 2 sets of polyatomic ion cards [for the ten
given]name formula [should still include charge…]name charge
Naming Covalent CompoundsPrefixes are used to show how many of which
atoms = number terms from Greek / Latin
Write the name of the cation [or most positive]only add a prefix for the first atom if
there is more than oneWrite the name of the anion [or most
negative]add a prefix to tell how many are presentchange the ending to -ide
Numbering Prefixes1 – Mono-2 – Di-3 – Tri-4 – Tetra-5 – Penta-
6 – Hexa-7 – Hepta-8 – Octa-9 – Nona-10 – Deka-
Practice What is the name for N2O4?
non-metal + non-metal…so covalentDinitrogen Tetraoxide
What is the name for Na2S?metal + non-metal = ionicSodium Sulfide
What is the name for CO2?non-metal + non-metal = covalentCarbon Dioxide
Practice – cont’dWhat is the name for (NH4)2O?
[hint: you need to know what (NH4) is…]Nitrogen Hydrogen OxideMononitrogen Tetrahydrogen OxideAmmonium OxideDiammonium OxideAmmonium Oxalate
CORRECT!!!!
Practice – cont’d