Understanding Formulas
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Two Classes of Elements
What Are Stable Elements?
Stabilizing Sodium
Stabilizing Oxygen
Sodium Loses electrons to Oxygen
Oxidation Numbers
Key Elements
• Examples
Two Classes of Elements
What are the Two Main Classes of Elements?
Metals and Nonmetals
Noble Elements
What Makes Elements Stable?
Losing or Gaining e-1.
Do metals Lose or Gain e-1?
Do nonmetals Lose or Gain e-1?
(Lose e-1) Oxidation
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10
Reduction (Gain e-1)
Stabilizing Sodium
How many e-1 for Na?
11e-1
What is the noble element closest to Na?
Ne
How many e-1 for Ne?
10e-1
Sodium loses/gains how many electrons?
1e-1
Na Na+1 + e-1
Oxidation or reduction?
(protons) + (electrons)=charge
(+11)
(-10)
+1
Stabilizing Oxygen
How many e-1 for O?
8e-1
What is the noble element closest to O?
Ne
How many e-1 for Ne?
10e-1
Oxygen loses/gains how many electrons?
2e-1
O + 2e-1  O-2 Oxidation or reduction?
(protons) + (electrons)=charge
(+8)
(-10)
-2
Sodium Loses electrons to Oxygen
Na Na+1 + e-1 (Stable Like Neon) Ox or Red?
O + 2e-1 O-2 (Stable Like Neon) Ox or Red?
How many sodium atoms are needed to satisfy
oxygen’s electron hunger? High Electronegativity
2e-1 means two Na
How many oxygen atoms are needed to satisfy
sodium’s electron loss?
Low Electronegativity
2e-1 means one O
Na2O
Oxidation Numbers
All elements Lose or Gain e-1.
Some have multiple loss or gain possibilities.
Fe+2
Fe+3
S-2
S+4
S+6
Key Elements
(99%) H+1
H-1
(99%) O-2
O-1
(Always) Li+1, Na+1, K+1, Rb+1, Cs+1, Fr+1
(Always) Be+2, Mg+2, Ca+2, Ba+2, Sr+2, Ra+2
(Always) Al+3
(with only a metal) F-1, Cl-1, Br-1, I-1
(NO3-1) ion is always +5
(SO4-2) ion is always +6
Example One
Finding Oxidation Numbers
sum of the oxidation #’s = zero
+3 -2
Find Ox #’s for Al2S3?
2 (Al)+ 3(S) = Zero
2 (+3)+ 3(S) = Zero
S = -2
Example Two
Finding Oxidation Numbers
sum of the oxidation #’s = zero
+2 +5 -2
Find Ox #’s for Ca3(PO4)2?
3(Ca)+2(P)+ 8(O) = Zero
3(+2)+ 2(P)+ 8(-2) = Zero
P = +5
Finding Oxidation #’s for Compounds
+1 -2
H2O
+1+4 -2
H2CO3
+1+5 -2
H3PO4
-3 +1+4 -2
(NH4)2CO3
+2 +5 -2
Ca3(AsO4)2
+3 +6 -2
Fe2(SO4)3
+2 +7 -2
Ba(ClO4)2
+1+5 -2
HNO3
+1+6 -2
H2SO4
+1 +6 -2
Hg2SO4
+1 +6 -2 +3 +4 -2
Na2Cr2O7 Al2(CO3)3
Writing and Naming fromulas
• Naming Formulas
• Writing Formulas
Naming Inorganic Salts
TWO parts to the name
1) Cation Positive
2) Anion Negative
Cation Examples
Ca+2 Al+3
Fe+2
Na+1
Anion Examples
Cl-1 NO3-1 SO4-2
N-3
Example One
Name the formula Fe2(CrO4)3
Step #1 Find The + Ion(s).
Iron(II) Fe+2
Iron(III) Fe+3
Example One
Step #2 Find The - Ion(s)
Chromate CrO4-2
Example One
Fe2(CrO4)3
Fe+2 Iron(II) Fe+3 Iron(III) CrO4-2Chromate
Iron(II) Chromate
Fe+2
CrO4-2
X (+2) + Y (-2) = 0
X=1
Y=1
1 (+2) + 1 (-2) = 0
FeCrO4
Iron(III) Chromate
Fe+3
CrO4-2
X (+3) + Y (-2) = 0
X=2
Y=3
2 (+3) + 3 (-2) = 0
Fe2(CrO4)3
Example Two
Al2(CO3)3
Al+3 Aluminum CO3-2 Carbonate
Aluminum Carbonate
Al+3
CO3-2
X (+3) + Y (-2) = 0
X=2
Y=3
2 (+3) + 3 (-2) = 0
Al2(CO3)3
Naming a Formula
Name Fe(IO4)2
Iron(III) periodate
Iron(II) periodate
(Fe+3)_(
1 IO4-1 )_
3
(Fe+2)_(
1 IO4-1 )_
2
Fe(IO4)3
Fe(IO4)2
Name Sn(HPO4)2
tin(II) hydrogen phosphate (Sn+2)_(
2 SnHPO4
2 HPO4-2 )_
tin(IV) hydrogen phosphate (Sn+4)_(
2 HPO4-2)_
4 Sn(HPO4)2
Naming Example Three
Sn3(BO3)4
Sn+4 Tin(IV)
BO3-3 Borate
Tin(IV) Borate
Sn+4
BO3-3
X (+4) + Y (-3) = 0
X=3
Y=4
3 (+4) + 4 (-3) = 0
(Sn+4)_(
3 BO3-3 )_
4
Sn3(BO3)4
Writing a Formula From a Name
Sodium Carbonate
(Na+1)_(
2 CO3-2 )_
1
Na2CO3
Aluminum phosphite
(Al+3 )_(
3 PO3-3 )_
3
AlPO3
Calcium Arsenate
(Ca+2)_(
2
3 AsO4-3 )_
Ca3(AsO4)2
Writing a Formula From a Name
X (+?) + Y (-?) = 0
(Cation+?)X(Anion-?)Y
If X or Y is 2 or greater...
and the ion is polyatomic.
Ba+2 Cr2O7-2 Hg2+2
Lowest Whole Number Ratio
Pb+4
Lithium Nitrate
(Li+1 )_(
1 NO3-1 )_
1
Hydrogen Phosphate (H+1 )_(
3 PO4-3 )_
1
Ammonium carbonate ( NH4+1 )_(
1
2 CO3-2)_
Calcium Arsenate
(Ca+2)_(
2
3 AsO4-3 )_
Iron(III) periodate
(Fe+3)_(
1 IO4-1 )_
3
Mercury(I) Sulfate
(Hg2+2)_(
2 SO4-2 )_
2
Barium Perchlorate (Ba+2 )_(
2
1 ClO4-1 )_
Sodium Dichromate (Na+1)_(
1
2 Cr2O7-2 )_
Lead(IV) Sulfate
(Pb+4)_(
4
2 SO4-2 )_
LiNO3
H3PO4
(NH4)2CO3
Ca3(AsO4)2
Fe(IO4)3
Hg2SO4
Ba(ClO4)2
Na2Cr2O7
Pb(SO4)2