Unit01_Alchemy_Sect4.ppt - mrshuddie

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Unit01_Alchemy_Sect4.ppt - mrshuddie Powered By Docstoc
					Section IV: Moving Electrons
Lesson 17 Technicolor Atoms
Lesson 18 Life on the Edge
Lesson 19 Noble Gas Envy
Lesson 20 Getting Connected
Lesson 21 Salty Eights
Lesson 22 Isn’t It Ionic?
Lesson 23 Alchemy of Paint
Lesson 24 Shell Game
Lesson 17: Technicolor Atoms
Flame Tests
ChemCatalyst
These drawings are models that show solid copper,
solid copper chloride, and aqueous copper chloride
as collections of atoms.




Cu(s)          CuCl2(s)                     CuCl2(aq)
Solid copper   Solid copper (II) chloride   Aqueous copper (II) chloride


1. Describe each model.
2. What is similar about each model? What is
different?
Key Question
What evidence is there that certain atoms are
present in a compound?
You will be able to:
•   conduct a flame test and use the results to
    determine the identity of a compound
•   interpret evidence of the presence of certain
    atoms within compounds
Prepare for the Lab
Work in groups.
You will be using chemicals and fire today.
Follow safety instructions.
    Wear safety goggles.
    Tie back long hair and remove dangling
    jewelry.
    Roll up long sleeves and keep clothing away
    from flames.
    Locate the eye wash, fire blanket, and fire
    extinguisher before starting the lab.
Discussion Notes
The metal element in each chemical formula
appears to be responsible for the flame colors.

Only certain elements produce colorful flames.

Flame test: A test used in the laboratory to look for
the presence of certain metal atoms. A sample of a
compound is heated in a flame, and the resulting
color is noted.
Discussion Notes (cont.)
Elements and compounds are collections of atoms.

The only way to change one atom into another is to
change the nucleus through a nuclear reaction.
Discussion Notes (cont.)
Sodium Atom, Na
Discussion Notes (cont.)
The illustration indicates that the flame colors are
associated with movements of the electrons within
the sodium atom.

Bohr’s model of the atom came directly from
evidence similar to that produced in class today.
Wrap Up
What evidence is there that certain atoms are
present in a compound?
 • Many metal atoms produce a characteristic
   colored flame when compounds containing those
   atoms are heated in a flame.
 • Flame tests are evidence that elements and
   compounds are collections of atoms.
Check-in
Predict the flame colors produced when heating
these substances. Explain your thinking.
• copper (II) carbonate
• calcium chloride
Lesson 18: Life on the Edge
Valence and Core Electrons
ChemCatalyst
1.   What do you notice
     about the number
     of spokes on the
     circles?
2.   The spokes
     represent
     electrons. Do the
     spokes represent
     the total number of
     electrons? Explain
     your thinking.
Key Question
Why do elements in the same group in the periodic
table have similar properties?
You will be able to:
• create a shell model diagram of an atom,
  placing the correct number of electrons in the
  correct shells
• explain the difference between a valence
  electron and a core electron
• describe the patterns in the periodic table
  associated with electron arrangements
Prepare for the Activity
Work in pairs.
Prepare for the Activity (cont.)
The Shell Model


                  The surface of each
                  sphere represents an
                  area where an electron
                  or a group of electrons
                  is most likely to be found.
Prepare for the Activity (cont.)
Electron shells are the levels around the nucleus
where electrons can be found.




 Sodium and magnesium have electrons in three electron shells.
Discussion Notes
The atomic number of an element is the same as
the total number of electrons.

The period (row) number of the element is the
same as the number of electron shells.

For main-group elements, the group number of the
element is the same as the number of electrons in
the outermost shell.
Discussion Notes (cont.)
Table of Valence and Core Electrons
Discussion Notes (cont.)
Valence shell: The outermost electron shell in an
atom.
Valence electrons: The electrons located in the
outermost electron shell of an atom.
Core electrons: All other electrons in an atom
besides the valence electrons.
Discussion Notes (cont.)
The arrangement of electrons in their shells is
highly predictable.

The numbers of core electrons also exhibit
patterns across each row of the periodic table.
Wrap Up
Why do elements in the same group in the periodic
table have similar properties?
 • Electrons occupy distinct areas around the
   nucleus called electron shells. The arrangement of
   electrons in these shells is highly predictable.
 • For main group elements, elements in the same
   group have the same number of valence
   electrons.
 • The number of valence electrons increases across
   a period.
 • The number of shells and the number of core
   electrons increase as you go down a group.
Check-in
Provide each piece of information for element 34.
a. The element’s name and symbol.
b. The total number of electrons in an atom of
   this element.
c. The number of core electrons in an atom of
   this element.
d. The number of valence electrons.
e. The group number for this element.
f. The names of other elements with the same
       number of valence electrons.
Lesson 19: Noble Gas Envy
Ions
ChemCatalyst
Chemists have found that
metal atoms transfer
electrons to nonmetal atoms
when they form compounds.
Examine the shell model
showing how a lithium atom
might transfer an electron to
a fluorine atom.



1. What effect does this electron transfer have on
   the charge of each atom?
2. What element does each atom resemble after
   the electron has been transferred?
Key Question
How is chemical stability related to the
arrangements of electrons in atoms?
You will be able to:
•   explain that an ion is formed when an atom
    loses or gains electrons and state the difference
    between a cation and an anion
•   determine the charge on an ion based on an
    atom’s placement in the periodic table
•   explain the relationship between ion charge and
    valence electrons
Prepare for the Activity
Work in groups of eight.

Ion: An atom (or group of atoms) that has a
positive or negative charge because it has lost or
gained electrons.
Discussion Notes
The table of arranged ion cards shows that the charges on
ions are quite predictable.
Discussion Notes (cont.)
When electrons are removed from or added to an
atom, the rest of the atom stays the same.

The charge on an ion is noted with a superscript.
Discussion Notes (cont.)
Cation: An ion with a net positive charge. Usually
these are formed from metal atoms.

Anion: An ion with a net negative charge. Usually
these are formed from nonmetal atoms.
Discussion Notes (cont.)
Electron arrangements
of atoms in ionic
compounds resemble
noble gases.
Discussion Notes (cont.)
Atoms tend to lose or gain electrons to attain the
electron arrangement of a noble gas.
Wrap Up
How is chemical stability related to the
arrangements of electrons in atoms?
 • When atoms gain or lose electrons, they form
   ions. Ions are atoms that carry a net positive or
   net negative charge.
 • When atoms lose electrons, they have a positive
   charge and are called cations.
 • When atoms gain electrons, they have a
   negative charge and are called anions.
 • Ions have electron arrangements resembling
   those of the noble gas atoms.
Check-in
1. Draw a shell model for calcium, Ca, showing
   the arrangement of its electrons.
2. What would have to happen for an atom of
   calcium to have an electron arrangement
   like that of a noble gas? Explain.
Lesson 20: Getting Connected
Ionic Compounds
ChemCatalyst
Metal elements combine with the nonmetal element
chlorine, Cl, to form compounds. The formulas are given in
the tables.

Element   Compound   Element   Compound   Element   Compound


  Na       NaCl        Mg       MgCl2       Ne       none

   K        KCl        Ca       CaCl2       Ar       none

1. Compare the three tables. What do you notice?
2. Predict the formula of a compound formed between
lithium, Li, and chlorine, Cl. Which table would you put it
in?
Key Question
How can valence electrons be used to predict
chemical formulas?
You will be able to:
•   predict the chemical formulas of compounds
    that will form between metal and nonmetal
    atoms
•   explain how an ionic compound forms and
    determine whether it follows the rule of zero
    charge
Prepare for the Activity
Work in pairs.

Ionic compound: An ionic compound is a
compound composed of positive and negative ions,
formed when metal and nonmetal atoms combine.
Discussion Notes
Mg2+ + Cl– + Cl– produces MgCl2 with zero charge.
Discussion Notes (cont.)
Metal and nonmetal elements combine to form
ionic compounds.

The electron arrangements of the cations and
anions resemble the arrangements of a noble gas
atom.
Discussion Notes (cont.)
The rule of zero change can be used to determine
the chemical formulas of ionic compounds.

Rule of zero charge: In an ionic compound, the
positive charges on the metal cations and the
negative charges on the nonmetal anions sum to 0.
 Discussion Notes (cont.)
 Chemical Formulas of Ionic Compounds
           Number      Number
                                    Total
              of          of
                                   number      Total       Total
           valence     valence                                       Total
Example                               of      positive   negative
          electrons   electrons                                     charge
                                   valence    charge      charge
            for the     for the
                                  electrons
             metal    nonmetal
 NaF         1           7           8          +1         –1         0
 MgO         2           6           8          +2         –2         0
  AlN        3           5           8          +3         –3         0
 K2Se        1           6           8         2(+1)       –2         0
 MgCl2       2           7           16         +2        2(–1)       0
 AlF2        3           7           24         +3        3(–1)       0
 AL2O2       3           6           24        2(+3)      3(–2)       0
Discussion Notes (cont.)
The number of electrons associated with the atoms
of an ionic compound generally totals 8 or a
multiple of 8.
Wrap Up
How can valence electrons be used to predict
chemical formulas?
 • Metal atoms and nonmetal atoms combine to
   form ionic compounds.
 • In ionic compounds, the metal is considered a
   cation, and the nonmetal is considered an anion.
 • The charges on the cations and the anions in
   ionic compounds sum to 0.
 • Metal atoms and nonmetal atoms usually
   combine in ratios that result in a total of eight
   valence electrons or a multiple of eight valence
   electrons.
Check-in
What elements will combine with strontium, Sr,
in a 1:1 ratio? Explain your thinking.
Lesson 21: Salty Eights
Formulas for Ionic Compounds
ChemCatalyst
Find these cards in
Your Salty Eights
card deck.




1. List the ionic compounds you can make with pairs of
cards, using two different elements.
2. List the ionic compounds you can make with three cards
and only two different elements.
3. What rule must all these compounds satisfy?
Key Question
How can you predict chemical formulas and name
ionic compounds?
You will be able to:
•   use valence electrons to predict ionic
    compounds
•   develop proficiency at naming binary ionic
    compounds and writing their chemical formulas
Prepare for the Activity
Work in groups of four.
Discussion Notes
In general, atoms come together to form an ionic
compound if the number of valence electrons totals
8 or a multiple of 8.
Discussion Notes (cont.)
Writing correct chemical formulas is a matter of
keeping track of exactly how many atoms come
together to make a compound.

Creating correct chemical names is a matter of
remembering some basic guidelines.
Wrap Up
How can you predict chemical formulas and name
ionic compounds?
 • Ionic compounds tend to form from atoms that
    together have a total of 8 (or a multiple of 8)
    electrons in their outermost (valence) shells.
 • Noble gases already have eight valence
    electrons and don’t combine with other elements
    to make new compounds. They are already
    highly stable.
Check-in
Which of these compounds are likely to form?

a. Na2S      b. K2Mg      c. AlBr2

d. Na3N      e. OCl       f. CaO
Lesson 22: Isn’t It Ionic?
Polyatomic Ions
ChemCatalyst
The cards show a sodium ion and three polyatomic ions.




1. What do you think a polyatomic ion is?
2. Name three compounds formed between sodium ions
   and each of the three polyatomic ions. Use the rule of
   zero charge to write the compounds’ formulas.
Key Question
What is a polyatomic ion?
You will be able to:
•   recognize and name polyatomic ions
•   write names and chemical formulas of
    compounds with polyatomic ions
Prepare for the Activity
Work in pairs.

Ionic compound: An ionic compound is a
compound composed of positive and negative ions,
formed when metal and nonmetal atoms combine.
Discussion Notes
Polyatomic Ions
Discussion Notes (cont.)
Polyatomic ions contain more than one atom.

Most polyatomic ions are anions, with negative
charges.

Polyatomic ion: An ion composed of a group of
atoms with an overall positive or negative charge.
Most polyatomic ions are anions.
Discussion Notes (cont.)
The rule of zero charge can be used to predict the
formulas of compounds that contain polyatomic
ions.
Discussion Notes (cont.)
Compounds containing polyatomic ions have their
own unique naming guidelines.

          Polyatomic ion    Name

               OH–         hydroxide

              NO3–          nitrate

              CO32–        carbonate

              SO42–         sulfate

              NH4+         ammonium
Wrap Up
What is a polyatomic ion?
• Polyatomic ions are ions composed of a group
  of atoms. The charge is shared by all the
  atoms.
• To write the formula of an ionic compound that
  contains polyatomic ions, use the rule of zero
  charge.
• When naming compounds containing
  polyatomic ions, simply insert the name of the
  ion.
Check-in
1. What is the name of the compound
   Be(NO3)2?
2. What ions are present in this compound,
   and what are the charges on the ions?
Lesson 23: Alchemy of Paint
Transition Metal Chemistry
ChemCatalyst
1. What types of substances will you be creating
   in today’s lab?
2. What safety precautions are especially
   important for today’s lab?
3. Describe one of the procedures you will be
   completing in class today.
Key Question
What types of compounds are made from transition
metals?
You will be able to:
•   recognize transition metal compounds and their
    names
•   determine the charge on transition metal ions
    given their chemical formula
Prepare for the Lab
Work in groups of four.
You will be working with transition metal
compounds and acid. Follow lab safety guidelines.
 • Wear safety goggles at all times.
 • When heating compounds in a test tube, keep
   the open end pointed away from yourself and
   others.
 • If any compound comes in contact with your
   skin, wash immediately with plenty of water.
 • Tie back long hair and loose clothing. Remove
   any dangling jewelry.
Prepare for the Lab (cont.)
To decant and filter a solid, fold filter paper
following instructions.
Discussion Notes
Many of the paint pigments that artists historically
used and continue to use are ionic metal-nonmetal
compounds.
Wrap Up
What types of compounds are made from
transition metals?
 • Many of the colorful pigments used in painting
    are formed from metal-nonmetal compounds
    with transition metal cations.
 • Paint pigments in famous paintings can be as
    valuable as gold. A compound or element does
    not have to be gold to be valuable.
Lesson 24: Shell Game
Electron Configurations
ChemCatalyst
These drawings show two different ways to
represent the arrangement of the electrons in
atoms of the element calcium, Ca.




1. Name at least two differences in the drawings.
2. Name at least two similarities in the drawings.
Key Question
What does the periodic table indicate about the
arrangements of electrons?
You will be able to:
•   describe the structure of an atom in terms of
    electron shells and subshells
•   use the periodic table to determine the electron
    arrangement in an atom and to write electron
    configurations
•   explain the organization of the periodic table in
    terms of the arrangements of electrons in
    subshells
Prepare for the Activity
Work in pairs.
Discussion Notes
The electron shells in the shell model of an atom (except
for n = 1) are divided into subshells.
  Shell   Number of electrons in the shell   Subshell   Number of electrons in the subshell

  n=1                    2                     1s                       2
                                               2s                       2
  n=2                    8
                                               2p                       6

                                               3s                       2
  n=3                   18                     3p                       6
                                               3d                       10
                                               4s                       2
                                               4p                       6
  n=4                   32
                                               4d                       10
                                               4f                       14
Discussion Notes (cont.)
In an electron configuration, the number indicates
the shell number, the letter indicates the subshell
within the shell, and the superscript indicates the
number of electrons in the subshell.

Electron configuration: A shorthand way to keep
track of all the electrons in an atom of an element
for all the subshells that have electrons. The
number of electrons in each subshell is shown as a
superscript.
Discussion Notes (cont.)
The periodic table is organized in subshell blocks.
Discussion Notes (cont.)
The order of filling subshells does not always
correspond to the numerical order of the subshells.

The elements in the different subshell blocks have
related properties.
Wrap Up
What does the periodic table indicate about the
arrangements of electrons?
 • Each electron shell in the shell model, except
   for
   n = 1, is divided into subshells.
 • Each subshell can hold a specific maximum
   number of electrons.
 • The periodic table can assist you in figuring out
   the placement of electrons in subshells.
 • Chemists keep track of electrons and the
   subshells they are in by writing electron
   configurations.
Check-in
Identify the element with this electron
configuration:


         1s22s22p63s23p64s23d104p3

				
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