Today

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Todays outline

• Molecules ions
• Chemical formulas (molecular, ionic, empirical)
• Naming compounds
• Molecular compounds
• Ionic compounds
• Acids bases

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A molecule is an aggregate of two or more atoms
in a definite arrangement held together by
chemical bonds
A diatomic molecule contains only two atoms
H2, N2, O2, Br2, HCl, CO
A polyatomic molecule contains more than two atoms
O3, H2O, NH3, CH4
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An ion is an atom, or group of atoms, that has a
net positive or negative charge.
cation ion with a positive charge If a neutral
atom loses one or more electrons it becomes a
cation.
anion ion with a negative charge If a neutral
atom gains one or more electrons it becomes an
anion.
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Do You Understand Ions?
13 protons, 10 (13 3) electrons
34 protons, 36 (34 2) electrons
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A monatomic ion contains only one atom
Na, Cl-, Ca2, O2-, Al3, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4, NO3-
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A molecular formula shows the exact number of
atoms of each element in the smallest unit of a
substance (one molecule)
An empirical formula shows the simplest
whole-number ratio of the atoms in a substance
H2O
CH2O
C6H12O6
O3
O
N2H4
NH2
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• ionic compounds consist of a combination of
  cations and an anions
• the formula is always the same as the empirical
  formula
• compounds do not actually exist as discrete
  molecular units

The ionic compound NaCl
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Formula of Ionic Compounds
For neutral ionic compounds, the charges must add
up to zero
KBr
K
Br-
CaI2
Ca2
I-
ZnS
Zn2
S2-
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Formula of Ionic Compounds
Al2O3
Al3
O2-
Na2CO3
Na
CO32-
Ca3(PO4)2
Ca2
PO43-
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Naming compounds

• Will talk about naming three classes of
  compounds
• Ionic compounds
• Molecular compounds
• Acids and bases

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Naming ionic compounds

• 1) name cation
• 2) list cation charge if more than one is
  possible
• 3) name anion

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Naming ionic compounds (cations)

• Ammonium cation (NH4)
• Metal cations
• Metal cations that have only one possible charge
  (Group 1A, Group 2A, Ag, Zn2, Cd2, Al3)
• Metal cations that have multiple possible charges
  (most transition metals)

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Transition metal cations

• Indicate charge in Roman numerals in parentheses
  after the metal
• Fe2 is called iron (II)
• Fe3 is called iron (III)
• Cu is called copper (I)
• Cu2 is called copper (II)

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Transition metal cations

• Another system -ic and -ous suffixes
• Fe2 is called ferrous
• Fe3 is called ferric
• Cu is called cuprous
• Cu2 is called cupric
• -ic is always for the higher charge
• -ous is always for the lower charge
• I will accept either naming system

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Naming ionic compounds (anions)

• Monatomic anions (-ide)
• Polyatomic anions (memorize)

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Putting it all together, to name ionic compounds

• 1) name cation
• 2) list cation charge if more than one is
  possible
• 3) name anion

Ba(OH)2
barium hydroxide
K2O
potassium oxide
Fe(OH)2
iron (II) hydroxide
KNO3
potassium nitrate
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hydrogen carbonate (or bicarbonate) HCO3-
carbonate CO32-
perchlorate ClO4-
chlorate ClO3-
chlorite ClO2-
hypochlorite ClO-
chromate CrO42-
dichromate Cr2O72-
cyanide CN-
dihydrogen phosphate H2PO4-
hydrogen phosphate HPO42-
phosphate PO43-
hydride H-
hydroxide OH-
hydrogen sulfate (or bisulfate) HSO4-
sulfate SO42-
sulfite SO32-
nitrate NO3-
nitrite NO2-
oxide O2-
peroxide O22-
permanganate MnO4-
thiocyanate SCN-
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Some trends
hydrogen carbonate (or bicarbonate) HCO3-
carbonate CO32-
dihydrogen phosphate H2PO4-
hydrogen phosphate HPO42-
phosphate PO43-
hydrogen sulfate (or bisulfate) HSO4-
sulfate SO42-
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Some trends
perchlorate ClO4-
chlorate ClO3-
chlorite ClO2-
hypochlorite ClO-
sulfate SO42-
sulfite SO32-
nitrate NO3-
nitrite NO2-
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Naming molecular compounds

• Usually nonmetallic elements
• Exist in discrete molecular units
• Naming procedure similar to ionic compounds
• 1) name 1st element
• 2) name 2nd element, adding -ide to the root
• 3) if more than one compound can be made from the
  same elements, use prefixes

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Molecular Compounds
HCl
hydrogen chloride
NF3
nitrogen trifluoride
SO2
sulfur dioxide
N2Cl4
dinitrogen tetrachloride
NO2
nitrogen dioxide
N2O
dinitrogen monoxide
Omit mono from first word Omit -a from prefix
for oxides
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Special exceptions

• Some compounds with hydrogen have nonsystematic
  names
• B2H6 borane
• CH4 methane
• SiH4 silane
• NH3 ammonia
• PH3 phosphine
• H2O water
• H2S hydrogen sulfide
• Memorize the ones in RED