Transcript periodic trends textbook

6.3
Periodic Trends
>
Trends in Atomic Size
Trends in Atomic Size
What are the trends among the elements
for atomic size?
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Periodic Trends
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Trends in Atomic Size
The atomic radius is one half of the distance
between the nuclei of two atoms of the same
element when the atoms are joined.
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Periodic Trends
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Trends in Atomic Size
Group and Periodic Trends in Atomic Size
In general, atomic size increases from
top to bottom within a group and
decreases from left to right across a
period.
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Periodic Trends
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Trends in Atomic Size
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Periodic Trends
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Trends in Atomic Size
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6.3
Periodic Trends
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Ions
Ions
How do ions form?
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Periodic Trends
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Ions
Positive and negative ions form when
electrons are transferred between atoms.
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Periodic Trends
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Ions
Positive and negative ions form when
electrons are transferred between atoms.
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Periodic Trends
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Ions
Some compounds are composed of particles
called ions.
• An ion is an atom or group of atoms that has
a positive or negative charge.
• A cation is an ion with a positive charge.
• An anion is an ion with a negative charge.
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Periodic Trends
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Trends in Ionization Energy
Trends in Ionization Energy
What are the trends among the elements
for first ionization energy, ionic size, and
electronegativity?
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Periodic Trends
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Trends in Ionization Energy
The energy required to remove an electron from
an atom is called ionization energy.
• The energy required to remove the first
electron from an atom is called the first
ionization energy.
• The energy required to remove an electron
from an ion with a 1+ charge is called the
second ionization energy.
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Periodic Trends
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Trends in Ionization Energy
Group and Periodic Trends in Ionization
Energy
First ionization energy tends to
decrease from top to bottom within a
group and increase from left to right
across a period.
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Periodic Trends
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Trends in Ionization Energy
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Periodic Trends
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Trends in Ionization Energy
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Periodic Trends
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Trends in Ionization Energy
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6.3
Periodic Trends
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Trends in Ionic Size
Trends in Ionic Size
During reactions between metals and
nonmetals, metal atoms tend to lose electrons,
and nonmetal atoms tend to gain electrons. The
transfer has a predictable effect on the size of
the ions that form.
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Periodic Trends
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Trends in Ionic Size
Cations are always smaller than the
atoms from which they form. Anions are
always larger than the atoms from
which they form.
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Periodic Trends
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Trends in Ionic Size
Relative Sizes of Some Atoms and Ions
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Periodic Trends
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Trends in Ionic Size
Size generally increases
Trends in Ionic Size
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6.3
Periodic Trends
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Trends in Electronegativity
Trends in Electronegativity
Electronegativity is the ability of an atom of an
element to attract electrons when the atom is in a
compound.
In general, electronegativity values
decrease from top to bottom within a
group. For representative elements, the
values tend to increase from left to
right across a period.
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Periodic Trends
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Trends in Electronegativity
Representative Elements in Groups 1A through 7A
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Periodic Trends
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Summary of Trends
Summary of Trends
What is the underlying cause of periodic
trends?
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Periodic Trends
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Summary of Trends
The trends that exist among these
properties can be explained by
variations in atomic structure.
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6.3
Periodic Trends
Summary of Trends
Increases
Decreases
Constant
Increases Decreases
Size
Electronegativity
Ionic
Atomic
Nuclear
Shielding
Ionization
of
size
cations
Size
anions
Charge
energy
>
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Section Assessment
Assess students’ understanding
of the concepts in Section 6.3
Continue to:
-or-
Launch:
Section Quiz
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6.3 Section Quiz
1. Which of the following sequences is correct
for atomic size?
a. Mg > Al > S
b. Li > Na > K
c. F > N > B
d. F > Cl > Br
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6.3 Section Quiz
2. Metals tend to
a. gain electrons to form cations.
b. gain electrons to form anions.
c. lose electrons to form anions.
d. lose electrons to form cations.
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6.3 Section Quiz
3. Which of the following is the most
electronegative?
a. Cl
b. Se
c. Na
d. I
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