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THE PERIODIC TABLE
AP CHEMISTRY
2010-2011
Ms. Paskowski
History of the Periodic Table
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Many early scientists organized the
elements in a table.
Mendeleev
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organized the elements according to physical
and chemical properties.
Correctly predicted the existence of previously
undiscovered elements and their properties
Figure 7.24 Mendeleev's Early
Periodic Table, Published in 1872
Periodic Trends
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Ionization Energy
Electron Affinity
Atomic Radius
Ionic Size
Valence Electrons
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Ionization Energy
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Energy required to remove an electron
from a gaseous atom or ion.
In general, as we go across a period from
left to right, the first ionization energy
increases.
In general, as we go down a group from
top to bottom, the first ionization energy
decreases.
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Ionization Energy

Why does the IE decrease down a group?

Why does the IE increase across a period?
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The effective nuclear charge increases across a
period and decreases down a column.
What is effective nuclear charge?
The Values of First Ionization Energy
for the Elements in the First Six Periods
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Concept Check


Explain why the graph of ionization energy
versus atomic number (across a row) is not
linear.
Where are the exceptions?
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Concept Check

Which atom would require more energy to
remove an electron? Why?
Li
Cs
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Concept Check

Which has the larger second ionization
energy? Why?
Lithium or Beryllium
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Successive Ionization Energies (KJ per
Mole) for the Elements in Period 3
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Electron Affinity
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Energy change associated with the
addition of an electron to a gaseous
atom.
In general as we go across a period from
left to right, the electron affinities
become more negative.
In general electron affinity becomes more
positive in going down a group.
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Figure 7.32 The Electron Affinity Values for
Atoms Among the First 20 Elements that
Form Stable, Isolated X- Ions
Atomic Radius


In general as we go across a period from
left to right, the atomic radius decreases.
In general atomic radius increases in
going down a group.
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Figure 7.33 The Radious of an Atom
(r) is Defined as Half the Distance
Between the Nuclei in a Molecule
Consisting of Identical Atoms
Concept Check

Which should be the larger atom? Why?
Na
Cl
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Concept Check
Which is larger?
 The hydrogen 1s orbital
 The lithium 1s orbital
Which is lower in energy?
 The hydrogen 1s orbital
 The lithium 1s orbital
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Atomic Radius of a Metal
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Atomic Radius of a Nonmetal
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Atomic
Radii for
Selected
Atoms
Exercise

Arrange the elements oxygen, fluorine, and
sulfur according to increasing:
 Ionization energy
 Atomic size
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Final Thoughts
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It is the number of valence electrons that
chemists use to explain an atom’s
chemistry.
BUT do not forget the involvement of the
nucleus.

Electrostatic interaction of positive and
negative charges is the fundamental force
that explains chemical interactions.

i.e., the nucleus of one atom MUST attract the
electrons of another atom to create a chemical
bond . . .
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