Binary Covalent Compounds

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Binary Covalent Compounds

• Composed of two non-metals
• can be same or different

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Two naming systems

• stock system
• system learned for ionic compounds
• uses roman
• traditional
• hear on news, see on ingredient lists
• sytem for naming molecules
• uses prefixes

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Both Naming Systems

• least electronegative of non-metal elements
  written first
• see table S

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Stock System

• 1st element must have Roman Numeral so
• figure out oxidation number

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Oxidation Number

• molecular substances DONT contain ions so use
  concept of oxidation for e- bookkeeping
• pretend all shared e- go to atom with higher
  electronegativity value
• atom with higher electronegativity value
  
• (-) oxidation
• atom with lower electronegativity value
  
• () oxidation

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7 Rules for Oxidation Numbers

• for free, uncombined element is 0

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for monatomic ion charge on ion
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Ca2 2 Cl-1 -1 Al3 3
fluorine is always (-)1
4 -1
CF4
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4.
Hydrogen is nearly always ()1, except when
bonded to metal, then (-)1
LiH CaH2 NaH
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• 5.
• Oxygen is nearly always (-)2 EXCEPT when

2 -1
OF2
-bonded to fluorine O is ()2
O22-
-in peroxide ion O is (-)1 (only with group 1
or 2 metals)
2 -1
MgO2
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6.

• sum oxidation numbers in neutral compound is 0

1 -2 4 -2 2
-2 6 -2
sum of oxidation numbers in polyatomic
ion charge of ion
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Naming Binary Covalent Compounds

• Stock System

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CO2

• CO2
• C goes first less electronegative than O

Each O is -2
CO2
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Try SO3
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Try N2O3
N2O3
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Naming Binary Covalent Compounds

• Traditional Naming System

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Traditional Naming

• less electronegative element named 1st
• stem 2nd element plus -ide ending
• prefixes tell how many of each element
• Exception NEVER start a name with mono-

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Prefixes Traditional System
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Traditional Naming
nitrogen monoxide