Honors Intergraded II

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Honors Intergraded II

• Chapter 4 The Structure of Matter

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Compounds and Molecules

• What are Compounds?
• Table salt is a compound made of two elements,
  sodium and chlorine.
• The compound has properties very different from
  those of the elements that make it.
• Chemical bonds distinguish compounds from
  mixtures.
• The attractive forces that hold different atoms
  or ions together in compounds are called chemical
  bonds.

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• Mixtures are made of different substances that
  are just placed together.
• Each substance in the mixture keeps its own
  properties.
• A compound always has the same chemical formula.
• Chemical structure shows the bonding within a
  compound.
• The arrangement of bonded atoms or ions within a
  substance is called chemical structure.

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• Two terms are used to specify the positions of
  atoms relative to one another in a compound.
• A bond length gives the distance between the
  nuclei of two bonded atoms.
• When a compound has three or more atoms, bond
  angles tell how these atoms are oriented.

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Models of Compounds

• Some models give you an idea of bond lengths and
  angles.
• Ball and stick model Figure 4-3.
• Structural formulas can also show the structures
  of compounds.
• Show the atoms chemical symbol and show the
  number of atoms and the arrangement of the atoms.
• Space-filling models show the space occupied by
  atoms Figure 4-4.
• The problem with this model is that it is harder
  to see bond lengths and angles.

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How does structure affect properties?

• Compounds with network structures are strong
  solids.
• Example Quartz (SiO2)
• Some networks are made of bonded ions
• Example Table salt (NaCl)
• Some compounds are made of molecules
• Example sugar (C12H22O11)

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• The strength of attractions between molecules is
  different for each compound because they have
  different properties.

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Ionic and Covalent Bonding

• When two atoms join a bond forms.
• Because there are so many different substances it
  makes sense that atoms can bond in different
  ways.
• What holds atoms together?
• Three different kinds of bonds describe the way
  atoms bond in most substances.
• The outermost energy level of a bonded atom is
  full of electrons.
• Atoms bond when their valence electrons interact.
  
• Bonds can bend and stretch without breaking.

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Ionic Bonds

• Ionic bonds are formed between oppositely charged
  ions.
• Atoms of metal elements, such as sodium and
  calcium, form the positively charged ions.
• Atoms of nonmetal elements, such as chlorine and
  oxygen, form the negatively charged ions.
• The transfer of electrons forms ionic bonds.

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• Example Na1 ion and Cl-1 ion ? NaCl
• Ionic compounds are in the form of networks, not
  molecules.
• The compound has a total charge of zero.
• When melted or dissolved in water, ionic
  compounds conduct electricity.

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Metallic Bonds

• Metals, like copper, can conduct electricity when
  they are solid.
• Metals are also flexible, so they can bend and
  stretch without breaking.
• Copper for example can be hammered flat into
  sheets (malleable) or stretched into very thin
  wire (ductile).

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• Electrons move freely between metal atoms
• Example Cu Cu ? Cu2

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Covalent Bonds

• Compounds that are made of molecules, like water
  and sugar have covalent bonds.
• Atoms joined by covalent bonds share electrons
• Example Cl2 share two electrons
• Bonds like this one in which electrons are shared
  equally are called nonpolar covalent bonds.

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• Atoms may share more than one pair of electrons
• Example O2 -four electrons shared
• Atoms do not always share electrons equally.
• An unequal sharing of electrons forms a polar
  covalent bond.

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Polyatomic Ions

• Polyatomic ion is an ion made of two or more
  atoms that are covalently bonded and that act
  like an single ion.
• There are many polyatomic ions Table 4-3 page 122
• Parentheses group the atoms of a polyatomic ion.

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• Some polyatomic anion names relate to their
  oxygen content.
• An -ate ending is used to name the ion with one
  more oxygen atom.
• The name of the ion with one less oxygen ends in
  -ite.

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Compound Names and Formulas.

• BaF2 barium fluoride
• BF3 boron trifluoride
• See that the names of these compounds reflect the
  two elements from which they are formed.

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Naming Ionic Compounds

• Names of ionic compounds include the ions of
  which they are composed.
• Some cation names must show their charge.
• Iron is a transition metal.
• Transition metals form several cation-each with a
  different charge iron (III) or iron (II)

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• Determining the charge of a transition metal
  cation

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Writing Formulas for Ionic Compounds

• List the symbols for each ion
• Write the symbols for the ion with the cation
  first
• Find the least common multiple of the ions
  charges
• Write the chemical, indicating with subscripts
  how many of each ion are needed to make a neutral
  compound

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Naming Covalent Compounds

• Numerical prefixes are used to name covalent
  compounds of two elements Table 4-7
• Chemical Formulas for Covalent Compounds
• Chemical formulas were determined by first
  measuring the mass of each element in the
  compound.

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• A compound's simplest formula is its empirical
  formula.
• This is the smallest whole-number ratio of atoms
  in the compound.
• Different compounds can have the same empirical
  formula.
• Formaldehyde, acetic acid and glucose (CH2O)

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• Molecular formulas are determined from empirical
  formulas.
• The molecular formula is a chemical formula that
  reports the actual number of atoms in one
  molecule of a compound.

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Organic and Biochemical Compounds

• The word organic has many different meanings.
• In chemistry the word organic is used to describe
  certain compounds.
• An organic compound is a covalently bonded
  compound made of molecules.
• Organic compounds contain carbon and almost
  always hydrogen.
• Other atoms, such as oxygen, nitrogen, sulfur,
  and phosphorus.

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• Carbon atoms form covalent bonds in organic
  compounds.
• When a compound is made of only carbon and
  hydrogen it is called a hydrocarbon.
• Alkanes have single covalent bonds (C-C)
• The simplest alkane is methane (CH4)
• See Table 4-9

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• The prefix gives the number of carbons
• Meth-one
• Eth two
• The ending ane denotes single bond between carbon
  atoms
• The pattern formula for alkanes is CnH2n 2
• This excluding cyclic alkanes which are ring
  structures

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Alkenes

• Alkenes have double carbon -carbon (CC) bonds.
• The simplest alkene is ethene (ethylene). The
  ending of all alkenes is ene.
• The pattern formula is CnH2n.

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Alkynes

• Alkyne have triple carbon - carbon (CC) bonds.
• The simplest alkyne is ethyne.
• The ending of all alkynes is -yne.
• The pattern formula is CnH2n-2.

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Alcohols

• Alcohols have -OH groups.
• They are made of oxygen as well as carbon and
  hydrogen.
• Simplest alcohol is methanol CH3OH.
• Ethanol C2H5OH.
• To make denatured alcohol methanol is added to
  ethanol .
• All alcohols have an ending of -ol.
• Alcohol molecules behave similarly to water
  molecules.

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• Substituted hydrocarbons replaces a hydrogen with
  another element
• Example CCl4 carbon tetrachloride.
• Aromatic hydrocarbons are unsaturated ring
  compound the simplest is benzene

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• Polymers are large molecules.
• Many polymers have repeating subunits. Example
  polyethene poly means many ethene.
• C2H4 many ethenes
• One C2H4 is a monomer
• Some polymers are natural, others are man made.
• Rubber, wood, cotton, wool, starch, protein, and
  DNA are all natural.
• Man made plastic or fibers.
• The elasticity of a polymer is determined by its
  structure.

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Biochemical Compounds

• Biochemical compounds are naturally occurring
  organic compounds that are very important to
  living things.
• Carbohydrates give you energy.
• Proteins form important parts of your body, like
  muscles, tendons, fingernail and hair.
• The DNA inside you gives your body information
  about what proteins you need.
• Each of these biochemical compounds is a polymer.

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• Many carbohydrates are made of glucose. Glucose
  provides energy.
• Starch is a polymer of glucose.
• Glucose is stored as glycogen in the body.
• Glucose, fructose, and galtacose are simple
  sugars monosaccharide C6H12O6
• Maltose, lactose, and sucrose are disaccharide
  C12H22O11

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• Proteins are polymers of amino acids.
• Amino acids are made of carbon, hydrogen, oxygen
  and nitrogen.
• Some amino acids also contain sulfur.
• There are 20 amino acids found in naturally
  occurring proteins.
• The way these amino acids combine determines
  which protein is made.
• Example of small protein is insulin.

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• DNA is a polymer with a complex structure.
• Your DNA determines your entire genetic makeup.
• DNA is paired chains.
• It has the shape of a twisted ladder known as a
  double helix.
• Your body has many copies of your DNA, every cell
  in your body has a copy of your genetic material
  (chromosome).

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• Copying cannot happen unless the two DNA strands
  are first separated.
• Proteins called helicases unwind DNA by
  separating the paired strands.
• Proteins called DNA polymerases then pair up new
  monomers with these already on the strand.
• At the end of this process, there are two
  identical strands of DNA.

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• The structure consist of alternating sugar
  molecules and phosphate units on side attached to
  each sugar is one of 4 possible DNA
  monomers-adenine, thymine, cytosine, or guanine.
  
• A-T or T-A G-C or C-G form the steps of the
  ladder.