LIVING BY
CHEMISTRY
Unit 1: ALCHEMY
Matter, Atomic Structure, and Bonding
In this unit you will learn:
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what matter is composed of
to use the language of chemistry
to decode information contained in the periodic table
how new substances with new properties are made
what holds substances together
Section IV: Moving Electrons
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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)
Solid copper
CuCl2(s)
Solid copper (II) chloride
CuCl2(aq)
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:
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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.
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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.
2.
What do you notice
about the number
of spokes on the
circles?
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:
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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 (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
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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:
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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:
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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
Example
Number
of
valence
electrons
for the
metal
Number
of
valence
electrons
for the
nonmetal
Total
number
of
valence
electrons
Total
positive
charge
Total
negative
charge
Total
charge
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,
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in a 1:1 ratio? Explain your thinking.