Molecules, Ions, and Their Compounds

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Molecules, Ions, and Their Compounds
Chapter 3
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Molecules and Molecular Compounds
Molecular and Empirical Formulas
Molecular formula A formula which gives the
actual number and type of atoms in a
molecule. Examples H2O, CO2, CO, CH4, H2O2, O2,
O3, and C2H4. Empirical formula A formula
which gives the lowest whole number ratio of
atoms in a molecule. Examples Substance Mol.
formula Empirical Formula Ethane
C2H6 CH3 Water H2O H2O
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Molecules and Molecular Compounds
Molecular and Empirical Formulas Condensed
formula A formula which indicates how atoms are
grouped together in a molecule. Name Molecular
Formula Condensed formula Ethane
C2H6 CH3CH3 Diethyl
ether C4H10O CH3CH2OCH2CH3
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Molecules and Molecular Compounds

• Picturing Molecules
• Structural Formula A formula which shows how
  the atoms of a molecule are joined.
• Structural formulas do not necessarily show the
  three dimensional shape of the molecule.

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Molecules and Molecular Compounds
Molecular Models These are three-dimensional
representations of molecules.
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Ions and Ionic Compounds

• If an electron is removed or added to a neutral
  atom a charged particle or ion is formed.
• A positively charged ion is called a cation.

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Ions and Ionic Compounds

• If an electron is removed or added to a neutral
  atom a charged particle or ion is formed.
• A positively charged ion is called a cation.
• A negatively charged ion is called an anion.

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Ions and Ionic Compounds

• Predicting Ionic Charge
• Metals tend to form cations
• Non-metals tend to form anions.

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Ions and Ionic Compounds

• Molecules can also gain or lose electrons and
  form ions, They are called polyatomic ions.

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Ions and Ionic Compounds
Ion Name Formula Ion Name Formula
Peroxide O22- Sulfate SO42-
Triiodide I3- Sulfite SO32-
Ammonium NH4 Phosphate PO43-
Nitrate NO3- Acetate CH3CO2-
Nitrite NO2- Perchlorate ClO4-
Hydroxide OH- Permanganate MnO4-
Carbonate CO32- Dichromate Cr2O72-
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Ions and Ionic Compounds
Ionic Compounds Ionic Compound A compound that
contains positively charged ions and negatively
charged ions.
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Ions and Ionic Compounds

• Predicting Formulas
• Lets consider a compound containing Mg and N.
• The common charge on Mg is 2 (or Mg2).
• The common charge on N is 3 (or N3-).
• Since we want to make a neutral (uncharged)
  compound, the total charges from the cations and
  anions must cancel-out (or sum to zero).
• Therefore, Mg needs to lose 6 electrons (3 ? 2)
  and N gain those 6 electrons (2 ? 3-).
• The resulting formula is Mg3N2.

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Naming Inorganic Compounds

• Names and Formulas of Ionic Compounds
• Naming of compounds (nomenclature) is divided
  into
• organic compounds (those containing C)
• inorganic compounds (the rest of the periodic
  table).
• We will consider the naming rules of the
  Inorganic compounds.

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Naming Ionic Compounds
Names and Formulas of Ionic Compounds

• Cations
• Cations from metal atoms have the same name as
  the metal.
• If the cation can form more than one ion, the
  positive charge is indicated by a roman numeral
  in parenthesis.
• Cations of nonmetals end in ium.
• P3 phosphorium

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Naming Inorganic Compounds
Names and Formulas of Ionic Compounds
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Naming Inorganic Compounds
Names and Formulas of Ionic Compounds

• Anions
• Monoatomic anions have names formed by dropping
  the ending of the name of the element and adding
  ide.
• Polyatomic anions containing oxygen have names
  ending in ate or ite.
• Anions derived by adding H to an oxyanion are
  named by adding as a prefix the word hydrogen- or
  dihydrogen-.
• HSO4- Hydrogensulfate
• H2PO4- Dihydrogenphsophate

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Naming Inorganic Compounds
Names and Formulas of Ionic Compounds

• Anions
• Oxyanions There are rules for these, but they
  are confusing.
• Ion Name
• ClO4- perchlorate ion
• ClO3- chlorate ion
• ClO2- chlorite ion
• ClO- hypochlorite ion

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Naming Inorganic Compounds
Names and Formulas of Ionic Compounds

• Ionic Compounds
• Name the compound by naming the cation followed
  by the anion.

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Naming Inorganic Compounds

• Naming Binary Molecular Compounds
• Binary molecular compounds have two elements.
• The name of the left-most element is written
  first.
• If the elements are in the same group the lower
  element is written first.
• The name of the second element ends in ide.
• Prefixes are used to indicate the number of atoms
  of each element.

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Naming Inorganic Compounds
Naming Binary Molecular Compounds
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Naming Inorganic Compounds

• Naming Binary Molecular Compounds
• Binary molecular compounds have two elements.
• The name of the left-most element is written
  first.
• If the elements are in the same group the lower
  element is written first.
• The name of the second element ends in ide.
• Prefixes are used to indicate the number of atoms
  of each element.
• Mono is never used in the first element.

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Naming Inorganic Compounds

• N2O
• This is a molecular compound.
• The first element (N), just takes its name,
  Nitrogen.
• The second compound takes its name, ending in
  -ide, Oxide.
• Now we must consider how to show that there are
  two nitrogen atoms, use di- as a prefix.
• Dinitrogen Oxide

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Naming Inorganic Compounds

• N2O5
• This is a molecular compound.
• The first element (N), just takes its name,
  Nitrogen.
• The second compound takes its name, ending in
  -ide, Oxide.
• Now we must consider how to show that there are
  two nitrogen atoms, use di- as a prefix.
• Finally, we must consider how to show that there
  are five oxygen atoms, use penta- as a prefix.
• Dinitrogen Pentoxide

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Formulas, Compounds, and the Mole

• Formula and Molecular Weights
• Molecular weight
• The sum of the atomic weights of each atom in
  the molecular formula.
• Formula weight is the general term, molecule
  weight refers specifically to molecular compounds.

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Formulas, Compounds, and the Mole
Formula and Molecular Weights Formula weight
(FW) The sum of the atomic weights of each atom
in the chemical formula. Example CO2
Formula Weight 1(AW, carbon) 2(AW,
oxygen) Formula Weight 1(12.011amu)
2(16.0amu) Formula Weight 44.0 amu
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Formulas, Compounds, and the Mole

• Formula and Molecular Weights
• Chemistry trick
• The masses of the atoms are on a gram equivalent
  scale.
• 1 atom (average) 1 mole
• C 12.01 amu 12.01 g
• H 1.008 amu 1.008 g
• So, the mass of a single atom or a mole is
  numerically equvalent.

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Formulas, Compounds, and the Mole
Converting Between Mass, Moles, Molecules and
Atoms
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The Mole
Moles Numbers of Particles
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The Mole
Mass ? Moles
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The Mole
Moles ? Mass
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The Mole

• A sample of hormone, estradiol, C18H24O2,
  contains 3.0 x 1020 atoms of hydrogen. How many
  atoms of carbon does it contain?

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The Mole

• A sample of hormone, estradiol, C18H24O2,
  contains 3.0 x 1020 atoms of hydrogen. How many
  atoms of carbon does it contain?

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The Mole

• A sample of hormone, estradiol, C18H24O2,
  contains 3.0 x 1020 atoms of hydrogen. How many
  atoms of carbon does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many atoms of
  carbon does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many atoms of
  carbon does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many molecules
  of estradiol does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many molecules
  of estradiol does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many molecules
  of estradiol does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many molecules
  of estradiol does it contain?

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The Mole

• A sample hormone, estradiol, C18H24O2, contains
  3.0 x 1020 atoms of hydrogen. How many molecules
  of estradiol does it contain?

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Describing Compound Formulas
Percentage Composition from Formulas
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Describing Compound Formulas
Percentage Composition from Formulas
Example Calculate the percent oxygen in
CH3CH2OH. Formula weight of ethanol
2(12.01amu) 6(1.01amu) 1(16.00amu)
46.08amu Mass of oxygen 1(16.00amu)
16.00amu oxygen
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Describing Compound Formulas
Percentage Composition from Formulas
Example Calculate the percent oxygen in
CH3CH2OH. Formula weight of ethanol
2(12.01amu) 6(1.01amu) 1(16.00amu)
46.08amu Mass of oxygen 1(16.00amu)
16.00amu oxygen
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Empirical Formulas from Analyses
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Empirical Formulas from Analyses

• Analysis
• Hg ? 73.9
• Cl ? 26.1
• assume 100g sample
• Hg ? 73.9 g
• Cl ? 26.1g
• convert grams to moles
• Hg ? 73.9g / 200.59g/mol
• Cl ? 26.1g/ 35.45g/mol

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Empirical Formulas from Analyses

• Analysis
• Hg ? 73.9
• Cl ? 26.1
• assume 100g sample
• Hg ? 73.9 g
• Cl ? 26.1g
• convert grams to moles
• Hg ? 73.9g / 200.59g/mol 0.368 mol
• Cl ? 26.1g/ 35.45g/mol 0.736 mol

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Empirical Formulas from Analyses

• Analysis
• Hg ? 73.9
• Cl ? 26.1
• assume 100g sample
• Hg ? 73.9 g
• Cl ? 26.1g
• -convert grams to moles
• Hg ? 73.9g / 200.59g/mol 0.368 mol
• Cl ? 26.1g/ 35.45g/mol 0.736 mol
• -determine the empirical formula by using the
  moles of theelements to get the smallest whole
  number ratio of the elements.

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Empirical Formulas from Analyses

• Analysis
• Hg ? 73.9
• Cl ? 26.1
• assume 100g sample
• Hg ? 73.9 g
• Cl ? 26.1g
• convert grams to moles
• Hg ? 73.9g / 200.59g/mol 0.367 mol
• Cl ? 26.1g/ 35.45g/mol 0.736 mol
• determine the empirical formula by using the
  moles of theelements to get the smallest whole
  number ratio of the elements.

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Empirical Formulas from Analyses

• Analysis
• Hg ? 73.9
• Cl ? 26.1
• assume 100g sample
• Hg ? 73.9 g
• Cl ? 26.1g
• convert grams to moles
• Hg ? 73.9g / 200.59g/mol 0.368 mol
• Cl ? 26.1g/ 35.45g/mol 0.736 mol
• determine the empirical formula by using the
  moles of theelements to get the smallest whole
  number ratio of the elements.

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Empirical Formulas from Analyses

• Analysis
• Hg ? 73.9
• Cl ? 26.1
• assume 100g sample
• Hg ? 73.9 g
• Cl ? 26.1g
• convert grams to moles
• Hg ? 73.9g / 200.59g/mol 0.368 mol
• Cl ? 26.1g/ 35.45g/mol 0.736 mol
• determine the empirical formula by using the
  moles of theelements to get the smallest whole
  number ratio of the elements.

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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7.
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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7. Analysis C ?
10.4 S ? 27.8 Cl ? 61.7
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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7. Assume 100g
sample C ? 10.4g S ? 27.8g Cl ? 61.7g
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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7. Moles of each
element C ? 10.4g/12.011g/mol 0.866 mol S ?
27.8g/32.066g/mol 0.867 mol Cl ?
61.7g/35.453g/mol 1.74 mol
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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7. Moles of each
element C ? 10.4g/12.011g/mol 0.866 mol S ?
27.8g/32.066g/mol 0.867 mol Cl ?
61.7g/35.453g/mol 1.74 mol
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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7. Moles of each
element C ? 10.4g/12.011g/mol 0.866 mol S ?
27.8g/32.066g/mol 0.867 mol Cl ?
61.7g/35.453g/mol 1.74 mol
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Empirical Formulas from Analyses
Determine the empirical formula of the compound
with the following compositions by mass C,
10.4 S, 27.8, Cl, 61.7. Moles of each
element C ? 10.4g/12.011g/mol 0.866 mol S ?
27.8g/32.066g/mol 0.867 mol Cl ?
61.7g/35.453g/mol 1.74 mol
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Empirical Formulas from Analyses
Molecular Formula from Empirical Formula To
determine the molecular formula from an empirical
formula, you must have the molecular weight of
the substance.
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Empirical Formulas from Analyses
Molecular Formula from Empirical
Formula Empirical formula CH Empirical
formula weight 13.019 g/mol Molecular weight
78.114g/mol
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Empirical Formulas from Analyses
Molecular Formula from Empirical
Formula Empirical formula CH Empirical
formula weight 13.019 g/mol Molecular weight
78.114g/mol
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Empirical Formulas from Analyses
Molecular Formula from Empirical
Formula Empirical formula CH Empirical
formula weight 13.019 g/mol Molecular weight
78.114g/mol
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Empirical Formulas from Analyses
Molecular Formula from Empirical
Formula Empirical formula CH Empirical
formula weight 13.019 g/mol Molecular weight
78.114g/mol
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End of Chapter Problems
6, 8, 12, 14, 20, 22, 28, 32, 36, 42, 48, 54, 68,
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