Transcript Writing and Naming Chemical Compounds Ionic Compounds

Writing 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:
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Nitrate NO3Carbonate CO3-2
Sulfate SO4-2
Phosphate PO4-3
Hydroxide OHAcetate C2H3O2- (CH3COO-)
Ammonium NH4+
Remember polyatomic ions STAY
TOGETHER!!!!
Bonding Review:
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Ionic compounds are formed when a metal
transfers electrons to a nonmetal
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Cation (metal) + Anion (nonmetal) = Ionic bond
Cation (metal) + Polyatomic Ion = Ionic bond
Polyatomic ion + Anion (nonmetal) = Ionic bond
Polyatomic Ion + Polyatomic Ion = Ionic bond
Writing Formulas for Ionic
Compounds
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Rules:
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The symbol tells the element and the subscript
(little number to the right of the symbol) tells how
many of each element is in the formula
The cation (metal ion) or positively charged
polyatomic ion is always written first and the anion
(nonmetal ion) or negatively charged polyatomic
ion is always written second
Writing Formulas for Ionic
Compounds
1) Start by writing the cation 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
written 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!
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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:
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1) LiF
2) CaS
3) Cs2O
4) Al2O3
5) Na2S
6) AlCl3
7) K2O
Writing Ionic Formulas for
Compounds with Polyatomic Ions
Start by writing your anion and cation with their
charges separately
1)
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If your anion or cation is a polyatomic ion, place
parenthesis around it and put the charge on the outside of
the parenthesis
Ex: If you are writing the formula for sodium and
carbonate: Na+1 and (CO3)-2
2) Criss-cross the charges so that they become the
subscripts but drop the +/- signs
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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!
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1) aluminum and nitrate
2) magnesium and phosphate
3) ammonium and chlorine
4) calcium and acetate
5) sodium and hydroxide
Check Your Answers:
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Al(NO3)3
Mg3(PO4)2
(NH4)Cl
Ca(C2H3O2)2
Na(OH)
Oxidation Number Exceptions
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Since the oxidation numbers of transition
metals cannot be predicted by looking at the
group numbers, you will need to memorize
the oxidation numbers for these exceptions
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Ag+1
Zn+2
Cd+2
Hg2+2
Hg+2
mercury (I)
mercury (II)
These Roman
Numerals will
make since in
about 3 slides
Naming Binary Ionic
Compounds
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Binary means there are only two elements in
the compound
Rules for Naming:
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1) Name the metal
2) Shorten the name of the non-metal and add
the suffix “– ide”
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Ex: KCl would be named potassium chloride
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Now You Try!
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Name the following compounds:
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1) MgBr2
2) NaF
3) Al2O3
4) CdO
5) ZnS
6) Na2O
7) K3N
Check Your Answers:
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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
Transition metals
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Since the oxidation numbers of transition metals cannot be
predicted by looking at the group numbers, a roman numeral
must be used to name the oxidation state of the transition metal
in a compound
 Transition metals can have more than one oxidation number
(charge)
The only exception to this rule is when naming the transition
metals you were told to memorize (silver, zinc, cadmium,
mercury still 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!
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1) SnO
2) CuS
3) Hg2I2
4) CuI
5) PbO2
Check Your Answers:
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1) tin (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
transition metal?
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Same process as naming ionic compounds
only the Roman numeral is the oxidation
number, so use it as the charge!
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Iron (III) oxide
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EX: Fe+3 and O-2 is written Fe2O3
Now You Try!
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Write the formula for the following
compounds:
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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:
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1) SnCl4
2) PbO2
3) SnS
4) HgBr2
5) Hg2F
6) Cu3N2
7) FeI2
Naming Ionic Compounds with
Polyatomic Ions
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Rules for naming:
1) Name the metal or positively 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 positively
charged poly first followed by the negatively 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:
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Molecular compounds are formed when two
nonmetals form a covalent bond
These compounds are called molecules
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Covalent bonds are the result of atoms sharing
electrons
Nonmetal + nonmetal = molecule
Naming Molecular Compunds
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We use Greek Prefixes to indicate the number of
atoms of each element that are present
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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
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Rules for naming:
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1) Name the first element using the appropriate
prefix that indicates how many atoms are present
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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!
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1) CO2
2) N2O3
3) Cl2O
4) SO3
5) P4O10
Check Your Answers:
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1) carbon dioxide
2) dinitrogen trioxide
3) dichlorine monoxide
4) sulfur trioxide
5) tetraphosphorus decoxide
Naming Acids
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Compounds which have hydrogen written as the
cation and have the physical state (aq) written next
to them are acids
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These compounds are named hydro (nonmetal)ic
acid
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If any other physical state is noted, (g) (s) or (l), the
compound is named like a regular binary compound
EX: HCl (aq) is named hydrochloric acid
If a hydrogen is written in front of a polyatomic ion
the compound is named (poly)ic acid
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EX: H(NO3) (aq) is named nitric acid
Now You Try!
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1) HF (aq)
2) H2S (aq)
3) H3P (aq)
4) H2(SO4) (aq)
5) H3(PO4) (aq)
6) HBr (l)
Check Your Answers:
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1) Hydrofluoric acid
2) Hydrosulfuric acid
3) Hydrophosphoric acid
4) Sulfuric acid
5) Phosphoric acid
6) Hydrogen bromide
Diatomic Elements
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There are 7 elements that can’t exist as single
atoms in nature so they must be written as two
atoms when they are not combined into compounds
They are just called by their elemental names
You must MEMORIZE these:
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Hydrogen, H2
Oxygen, O2
Nitrogen, N2
Fluorine, F2
Chlorine, Cl2
Bromine, Br2
Iodine, I2
You can remember these:
H. BrONClIF