CH. 6

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CH. 6

• The Structure of Matter

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Ch. 6 Section 1 Notes

• Compounds and Molecules
• Pg. 177-182

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Chemical Bonds

• The forces that hold atoms or ions together in a
  compound are called chemical bonds.
• Can be broken, and the atoms rearrange

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Chemical Structure

• The structure of a building is the way the
  buildings parts fit together
• A compounds chemical structure is the way the
  atoms are bonded to make the compound

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• Some models represent bond lengths and angles.
• Bond length is the distance between the nuclei of
  two bonded atoms
• If a compound has 3 or more atoms, a bond angle
  (the angle formed by two bonds to the same atom)
  tells which way there atoms point.

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• Atoms are often represented by a ball-and-stick
  model to help you understand the compounds
  structure.
• Structural formulas also show the structures of
  compounds.
• Chemical symbols are used to represent the atoms
• Space-filling model is another way to represent a
  water molecule.
• Shows the space that the oxygen and hydrogen
  atoms take up, or fill

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• The chemical structure of a compound determines
  that properties of that compound.
• Compounds with network structures are strong
  solids.
• Ex quartz
• The strong bonds make the melting and boiling
  point of quartz and other minerals very high

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• Some networks are made of bonded ions.
• Ex Table Salt (NaCl)
• Found in the form of regularly shaped crystals
• Made of a repeating network connected by strong
  bonds
• Oppositely attracted ions
• High melting and boiling point

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• Some compounds are made of molecules.
• Ex sugar
• Molecules attract each other and form crystals
• Nitrogen, Oxygen, and Carbon Dioxide
• --Gases that are made of molecules
• --Atoms are strongly attracted to each other and
  are bonded

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• The strength of attractions between molecules
  varies.
• Sugar, water and Dihydrogen sulfide are all
  compounds made of molecules but have different
  properties
• The higher the melting point, the stronger the
  attraction between the atoms

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• Hydrogen Bond
• Oxygen atom of a water molecule is attracted to a
  hydrogen atom of another molecule
• Strong bonds within each water molecule
• Weaker attractions between water molecules

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Ch. 6 Section 2 Notes

• Ionic and Covalent Bonding
• Pg. 183-190

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Why do Chemical Bonds Form?

• Atoms join to form bonds so that each atom has a
  stable electron configuration.
• One similar to a noble gas
• There are two kinds of chemical bonding
• Ionic Bonding
• Covalent Bonding

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Ionic Compounds Covalent Compounds
Structure Network of bonded ions Molecules
Valence Electrons Transferred Shared
Electrical conductivity Good (when melted or dissolved) Poor
State at room temp. Solid Solid, liquid, or gas
Melting and boiling points Generally high Generally low
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Ionic Bonds

• Form from the attractions between such oppositely
  charged ions.
• Formed by the transfer of electrons
• Oppositely charged ions bond (NaCl)

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• Ionic compounds are in the form of networks, not
  molecules.
• The formula unit of one sodium ion and one
  chloride ion is NaCl
• NaCl ratio is 11
• CaF2 is 12
• When melted or dissolved in water,
• ionic compounds conduct electricity.
• Ions are free to move
• when not is solid form.

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Covalent Bonds

• Compounds that are made of molecules, such as
  water and sugar have covalent bonds.
• Atoms joined by covalent bonds share electrons.
• Usually form between nonmetal atoms.

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• Can be solid, liquid or gas
• Low melting points
• MOST do not conduct electricity (not charged)
• Example Cl2
• Each has 7 valence electrons.
• Share one electron to have 8 valence electrons
  and become stable.

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Atoms may share more than one pair of electrons.

• When drawing the electron dot diagram, a line
  means that there are 2 electrons being shared.
• If there is two lines , that is a double
  covalent bond (4 electrons being shared)
• A triple covalent bond is
• formed by bonding two
• nitrogen atoms
• (total of 6 electrons)

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Atoms do not always share electrons equally.

• When electrons are shared equally, they are
  called nonpolar covalent bonds.
• Ex Cl2
• When two atoms of different elements share
  electrons, the electrons are not shared equally
  and forms a polar covalent bond.
• Ex NH3

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Metallic Bonds

• Metals are flexible and conduct electric current
  well because their atoms and electrons can move
  freely throughout a metals packed structure.
• Atoms in metals such as copper form metallic
  bonds.

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Polyatomic Ions

• Acts as a single unit in a compound, just as ions
  that consist of a single atom do.
• Groups of covalently bonded atoms that have a
  positive or negative charge as a group.
• Both covalent and ionic bonds
• There are many common polyatomic ions.

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Parentheses group the atoms of a polyatomic ion.

• A polyatomic ions charge applies not only to the
  last atom in the formula but to the whole ion.
• A polyatomic ion acts as a single unit in a
  compound

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• Some names of polyatomic anions relate to the
  oxygen content of the anion.
• Most end with ite or ate
• -ate ending usually used to name an ion that
  has 3 oxygen atoms
• Examples sulfate (SO42), nitrate (NO3),
  chlorate (ClO3)
• 2 or less oxygen atoms have an ite ending
• Examples sulfite (SO32), nitrite (NO2),
  chlorite (ClO2)
• Hydroxide and Cyanide are exceptions to the rules.

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CH. 6 Section 3 Notes

• Compound Names and Formulas
• Pg. 191-196

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Naming Ionic Compounds

• Formed between cations and anions
• The names of ionic compounds consist of the names
  of the ions that make up the compounds.

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• Names of cations include the elements of which
  they are composed.
• Usually the name of the element
• Ex sodium forms a sodium ion

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• Names of anions are altered names of elements.
• The difference is the names ending
• Usually with the ending ide
• Compounds with Oxygen atoms have ate, or ite
  endings
• An ionic compound must have a total charge of
  zero.

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• Some cation names must show their charge.
• Transition metals may form several cations (each
  will have a different charge).
• Iron forms a 2 ion AND a 3 ion
• This is shown by placing the charge of the cation
  as a Roman numeral in parentheses.
• Iron (II) ion and Iron (III) ion
• FeO --- Iron (II) Oxide
• Fe2O3 --- Iron (III) Oxide

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Determining the charge of a transition metal
cation.

• The total charge of the compound MUST be zero.
• Fe2O3
• Three oxide ions have a total charge of 6-.
  (each oxygen ion has a charge of 2- 2-(3)6-)
• So, the total charge of the cation must be 6

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Writing Formulas for Ionic Compounds

• If you are given the compounds name you can
  find the formula
• If you are given the formula you can find the
  charge of each ion

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Naming Ionic Compounds Rules

• If you are given the Name
• 1. Find the symbol of each element
• 2. Find the charge of each ion
• 3. Criss-cross Method
• 4. If one of the ions is a Polyatomic Ion, put
  parentheses around it!!

• Calcium Chloride
• Ca, Cl
• Ca2 , Cl -1
• CaCl2
• This is not a polyatomic Ion
• This is a polyatomic Ion

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Naming Ionic Compound Rules

• If you are given the formula
• 1. Determine if the FIRST ion is a Transition
  metal. If so, you MUST find its charge!
• 2. Find the name of each of the ions
• 3. The cation is the same as it is on the
  periodic table
• 4. The anion has an ide ending (unless it is a
  polyatomic ion)

• AgF
• Since there is no subscript number the charges
  for both must be 1.
• Ag is Silver, F is Flourine.
• F is in group 17 and has a -1 charge so, Ag is
  the cation.
• Silver Flouride

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• To find the charge of ions in a chemical formula
• Determine the ratio of the given formula
• Separate the ions
• Determine each of their charges
• If the cation is a transition metal, use the
  criss-cross method and then look at its ratio.
• Compare to the original ratio. What ever you do
  to the first element, you must do the the 2nd.

• CrO2
• 12 ratio
• Cr O2
• Cr 4 O-2
• Cr2O4 Ratio is 24
• Reduce the ratio to 12

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• Math Skills Writing Ionic Formulas
• Practice Problems 1-3 Pg. 193
• Lithium oxide
• Li1 O-2
• Li2O
• Beryllium chloride
• Be2 Cl-1
• BeCl2
• Titanium (III) nitride
• Ti3 N-3
• TiN

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Naming Covalent Compounds

• For covalent compounds of two elements, numerical
  prefixes tell how many atoms of each element are
  in the molecule.
• Numerical prefixes are used to name covalent
  compounds of two elements.
• If there is only one atom of the first element,
  the name does not get a prefix.

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Number of Atoms Prefix
1 Mono-
2 Di-
3 Tri-
4 Tetra-
5 Penta-
6 Hexa-
7 Hepta-
8 Octa-
9 Nona-
10 Deca-
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• BF3
• Boron Trifluoride
• N2O4
• Dinitrogen tetroxide

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Empirical Formulas

• Chemical formulas that are unknown are determined
  by figuring out the mass of each element in the
  compound.
• Once the mass of each element is known,
  scientists can calculate the compounds empirical
  formula, or simplest formula.
• An empirical formula tells us the smallest
  whole-number ratio of atoms that are in a
  compound.

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• Different compounds can have the same empirical
  formula.
• Molecular formulas are determined from empirical
  formulas.
• A compounds molecular formula tells you how many
  atoms are in one molecule of the compound.
• Masses can be used to determine the empirical
  formula.
• Convert the masses to moles. Then, find the
  molar ratio to give you the empirical formula.

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• Pg.196
• Math Skills Finding Empirical Formulas
• One mole of an unknown compound has 36.04 g of
  Carbon and 6.04g of hydrogen. What is the
  compound empirical formula.

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Section 3 Review 1, 5

• Name the following ionic compounds, and specify
  the charge of any transition metal cations.
• FeI2
• Iron(II) Fluoride
• MnF3
• Manganese(III)Flouride
• CrCl2
• Chormium(II) Chloride
• CuS
• Copper(II) Sulfide

• 5. Determine the chemical formulas for the
  following ionic compounds.
• Magnesium sulfate
• MgSO4
• Rubidium bromide
• RbBr
• Chromium(II) fluoride
• CrF2
• Nickel(I) carbonate
• Ni2CO3

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Ch. 6 Section 4 Notes

• Organic and Biochemical Compounds
• Pg. 197-204

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Organic Compounds

• An organic compound is a covalently bonded
  compound that contains carbon.
• Most contain hydrogen.
• Oxygen, nitrogen, sulfur, and phosphorus can also
  be found in organic compounds.

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• Carbon atoms form four covalent bonds in organic
  compounds.
• A compound made of only hydrogen and carbon atoms
  is known as a hydrocarbon.
• Methane, CH4 is an example
• There are four single C-H bonds
• A carbon atom may never form more than 4 bonds at
  a time.

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• Alkanes are hydrocarbons that have only single
  covalent bonds.
• Can have C-C bonds as well as C-H bonds
• Methane is the simplest alkane

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Arrangements of carbon atoms in alkanes.

• The carbon atoms in methane, ethane, and propane
  are all bonded in a single line because that is
  their only possible arrangement.
• If there are more than 3 bonded carbon atoms in a
  molecule, the carbon atoms do not have to be in a
  single line.

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• IF they are in a single line the alkane is a
  normal alkane, or n-alkane.
• The condensed structural formula shows how the
  atoms bond.

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• Alkane chemical formulas usually follow a
  pattern.
• Except for cyclic alkanes
• The of Hydrogen atoms is always 2 more than 2x
  the of carbon atoms
• CnH2n2

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Alkenes have double carbon-carbon bonds.

• Hydrocarbons
• Have at least one double covalent bond between
  carbon atoms. CC
• Replace the ane ending with ene.
• Simplest alkene is ethene (ethylene)

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• Alcohols have hydroxyl (-OH) groups.
• Made of oxygen, hydrogen, and carbon
• Most alcohols end in ol

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• Alcohol and water molecules behave similarly.
• Methanol and methane are alike except that one of
  the hydrogen atoms is replace by a Hydroxyl group
• Alcohol molecules are attracted to each other
• Liquid at room temp HIGH boiling points

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Polymers

• A polymer is a molecule that is a long chain made
  of smaller molecules.
• Have repeating subunits
• Polyethene, is a polymer that makes up plastic
  milk jugs. Polymany
• Ethene is an alkene that has the formula C2H4.
• Polyethene means many ethenes
• The smaller molecule that makes up the polymer is
  called a monomer.

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• Some polymers are natural, and others are
  artificial.
• Natural Rubber, wood, cotton, wool, starch,
  protein, DNA, etc.
• Human-made Plastics or Fibers

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A polymers structure determines its elasticity.

• Chains are tangled and can slide past each other.
• When the chains are connected to each other, the
  polymers properties are different.
• Some are elastic (can stretch)
• When released, returns back to its original
  shape.
• Ex Rubber bands

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Biochemical Compounds

• Essential to life, include carbohydrates,
  proteins, and DNA
• Can be made by living things
• Carbohydrates give you energy
• Proteins form important parts of your body
• Muscles, tendons, fingernails, and hair
• The DNA inside your cells gives your body info
  about what proteins you need.

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Many carbohydrates are made of glucose.

• Carbohydrates include sugars and starches,
  provide energy to living things.
• Sucrose (table sugar) is made of two simple
  carbohydrates, glucose and fructose, bonded
  together.
• Starch is made of a series of bonded glucose
  molecules, and is a polymer.

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• When you eat starchy food the enzymes in your
  body break down the starch.
• The glucose that is not needed is stored as
  glycogen, a polymer of glucose.
• When active, glycogen breaks apart into glucose
  molecules and gives you energy.

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Proteins are complex polymers of amino acids.

• Proteins, which provide structure and function to
  parts of cells, are very complex.
• Made of many different molecules that are called
  amino acids.
• Made of carbon, hydrogen, oxygen, and nitrogen.
  Some contain sulfur.
• 20 amino acids found in naturally occurring
  proteins

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• The amino acids that make up a protein determine
  the proteins structure and function.
• Proteins are long chains made of amino acids.
• Made of thousands of bonded amino acid molecules

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DNA is a polymer that stores genetic information

• DNA is a very long molecule made of carbon,
  hydrogen, oxygen, nitrogen, and phosphorus.
• DNA is in the form of paired chains, or strands.
• Shape of a twisted ladder, double helix.

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• DNA is the information that the cell uses to make
  proteins.
• DNA monomers
• Adenine, thymine, cytosine, and guanine
• Pair with other DNA monomers that are attached to
  the opposite strand in a predictable way