C: Compounds

1
C Compounds

• Compounds. Huh?
• A compound is an electrically neutral substance
  that consists of two or more different elements
  with their atoms present in a definite ratio
• Compounds Terminology
• Binary Consists of only 2 elements
• Organic Contains Carbon and hydrogen
• Inorganic No Carbon

2
Compounds

• The atoms are bonded together due to a chemical
  change
• The resulting compound has physical and chemical
  properties different than either of the reactants
• Eg Hydrogen Oxygen Water
• Molecules Electrically neutral compounds formed
  by atoms bonded together
• Ions Positive or negatively charged atom or
  molecule

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Ions

• Cations Positively charged ions
• Anions Negatively charged ions
• Examples

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Ionic and Molecular Compounds

• Ionic Compound Ions form compound that is
  electrically neutral
• Usually formed by the reaction of a metal and a
  nonmetal
• Na(s) Cl(g) ? NaCl(s)
• Molecular Compound Binary molecular compounds
  are usually formed by the reaction of 2 nonmetals
• 2H2(g) O2(g) ? 2H2O (l)

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Formulas

• Chemical (or Molecular) Formula
• The composition of a compound with chemical
  symbols
• eg Water, Glucose
• Composition only! Doesnt give you an idea of
  how they are linked

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Formulas

• Structural Formula
• Two dimensional representation of how atoms in a
  molecule are linked together
• eg Ethanol

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Formulas

• Line Formula
• Organic chemists sometimes omit the
  carbon-hydrogen bonds knowing that carbon ALWAYS
  forms 4 bonds
• eg Ethanol

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Other Representations

• Spacefilling model
• All atoms are spheres and the spheres are stuck
  together
• Ball and Stick
• Atoms are balls and bonds are sticks

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Other Representations

• Density Isosurface
• The most probable location of the electrons
  across entire molecule is shown
• Electrostatic Potential Surface
• Show the distribution of electric charge across
  the density isosurface
• Blue-----------------------------gtRed
• Positive Negative

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Ionic Compounds

• An ion forms when a compound gains or loses
  electrons
• The tendency to do this will be explained in the
  next chapter
• Ionic compounds form by the association of these
  positive and negative ions

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How do Monatomic Ions form?

• In order to predict what type of ion an element
  will form, we need to look at the s and p blocks

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s block Element Ionization

• Elements in the s block will lose one or two
  electrons depending on their group
• Group 1 elements form monovalent cations
• Group 2 elements form divalent cations

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p block Element Ionization

• Elements in the p block will gain 1 to 3
  electrons depending on their group
• Take the group number of the element and subtract
  18 from it

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• Rule Atoms gain or lose electrons until they
  have the same number as the nearest noble gas
  element

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Polyatomic Ions

• Ions consisting of two or more atoms bonded
  together
• eg Cyanide
• Ammonium
• Carbonate
• Nitrate
• Sulfate

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Common Ions You MUST know
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Ionic Compounds

• In ionic compounds, the ions arent bonded
  together like they are in molecular compounds
• They are associated by electric charge
  interactions
• The chemical formulae of ionic compounds are
  referring to the Ratios of anions to cations
• eg NaCl 1 Na for every Cl-
• eg Na2CO3 2 Na for every CO32-
• We need to remember the polyatomic ions to help
  us identify which compounds are molecular and
  which are ionic

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How do we write the formula of an ionic compound?

• Step 1 Find the charge of the anion and the
  charge of the cation
• Step 2 Combine the ions in a ratio that negates
  the charges
• Example Sodium chloride
• Example Aluminum Oxide

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D The Nomenclature of Compounds
Common Name Historic name that gives no
identity of the composition eg Water,
bleach Systematic Name Scientific name that
reveals the composition of the compound (and
sometimes its structure) eg Dihydrogen oxide,
sodium hypochlorite
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Cations
Common Name For atoms with more than one
oxidation state (transition metals) Add -ous to
the lower charge state name Add -ic to the
higher charge state name Cu1 Cuprous
ion Fe2 Ferrous ion Cu2 Cupric ion Fe3
Ferric ion Scientific Name Use the element
name followed by Roman numerals matching the
charge state (What are the scientific names of
the ions above?)
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Anions
Monatomic ions are named by adding the suffix
-ide to the stem of the elements name (see
Fluoride, chloride, oxide, bromide, sulfide
above).
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Anions

• Oxoanions can exist as multiple species, and as
  such, require memorization
• One species of oxoanion Add the suffix -ate
  to the stem of the name
• Carbonate, CO32-
• Two species of oxoanion Add the suffix -ite
  to the stem of the species with the lower number
  of oxygens AND add the suffix -ate to the stem
  of the species with the higher number of oxygen
  atoms.
• Nitrite, NO2- Nitrate, NO3-
• Sulfite, SO32- Sulfate, SO42-

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Anions

• Oxoanions can exist as multiple species, and as
  such, require memorization
• Four species of oxoanion
• Add hypo- to the ite for of the name for the
  species with the lowest number of oxygen atoms
• Add per- to the -ate form of the name for the
  species with the highest number of oxygen atoms
• Hypochlorite, ClO- Chlorite, ClO2-
• Chlorate, ClO3- Perchlorate, ClO4-

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Anions

• Oxoanions can exist as multiple species, and as
  such, require memorization
• Anions with hydrogen
• Add hydrogen to the monatomic anion name
• HS-, Hydrogen sulfide
• HCO3-, hydrogen carbonate
• H2PO4-, Dihydrogen phosphate

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Naming Ionic Compounds

• Ionic compounds are named by starting with the
  name of the cation (and oxidation number if more
  than one is possible), followed by the name of
  the anion
• Hydrates are named by adding the word hydrate
  preceded by the Greek prefix indicating the
  number of water molecules in the formula unit
• Step 1 Identify the cation and the anion
• Step 2 Identify the charge of the cation by
  looking at the anion
• Step 3 Name the cation (include the oxidation
  number learned in step 2)
• Step 4 Add the anion name

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Naming Ionic Compounds
Examples NaCl CoCl3 MgCl26H2O Fe2(SO4)3
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Naming Inorganic Compounds (NOT Hydrocarbons!!!)
Name the element on the left and then add the
number and name of the element on the right
adding the suffix ide to the stem of the
element name
PCl3
Phosphorous trichloride
SF6
Sulfur hexafluoride
N2O
Dinitrogen oxide
N2O5
Dinitrogen pentoxide
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Naming Inorganic Compounds (NOT Hydrocarbons!!!)

• Exceptions!!!
• Phosphorous compounds because it can have
  multiple oxidation states
• Common compounds
• NH3 Ammonia
• N2O Nitrous oxide
• N2H4 Hydrazide
• H2O Water

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Summary of Naming Inorganic Compounds
Example Write the formula of chromium (III)
nitrate hexahydrate Example Write the formula
of dinitrogen tetraoxide Example What is the
systematic name of HNO2
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Names of Common Organic Compounds

• The names of organic compounds are based upon the
  names of the parent compounds above
• Alcohols contain -OH groups
• Carboxylic acids contain -COOH groups
• Haloalkanes contane halogens