Download Ionization Energy - Hicksville Public Schools

11/30/2016
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 What
Ionization Energy
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
Ionization Energy
 The ease with which valence
electrons can be added/removed
from an atom is an important
factor in determining it’s
chemical behavior
1st ionization energy, I1, is the
energy needed to remove the
1st valence electron from an atom,
forming a cation+1
I1
 Na(g) → Na+1(g) + e-
cathode?
cation?
anode?
anion?
Ionization Energy
 The ionization energy is the
energy required to remove an
electron from the ground state of
the atom when it is a gas
 The greater the ionization energy,
the more difficult it is to remove
an electron
Ionization Energy
 The
is the charge of a(n):
Ionization Energy
2nd ionization energy, I2, is
the energy needed to remove the
2nd valence electron forming a
cation+2, and so on…
I2
 Na+1(g) → Na+2(g) + e The
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Ionization Energy
Ionization Energy
that the ionization energies
for the elements increase as
additional electrons are removed:
 Notice
 I1
< I2 < I3 < …
 Why?
 As
each additional electron is
removed, the remaining electrons see
a larger effective nuclear charge!
Ionization Energy
the huge increase in ionization
energy that occurs when an core
electron is removed:
 Note
 Na → Na+1
 Na+1 → Na+2
I1 = 496 kJ/mol
I2 = 4560 kJ/mol
 Mg → Mg+1
 Mg+1 → Mg+2
I1 = 738 kJ/mol
I2 = 1450 kJ/mol
I3 = 7730 kJ/mol
 Mg+2 I2
→ Mg+3
Ionization Energy
 Removal of core electrons require
overcoming a much larger
effective nuclear charge
 Why?
 Disturbing the stability of an octet
 Na+1:
 Na+2:
Solution
Problem
 Predict
which of the 3 elements will
have the largest I2, based on their
position on the periodic table
[Ne] = 2-8
2-7
greatest ionization energies
involve the removal of core electrons
 The
2nd e- must be a core e The 1st e- must have been the only
valence e The
 Therefore,
we are looking for an
element with 1 valence electron
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Solution
 That
element is the one indicated
in red, Na
(4562 kJ/mol)
 Na
(1145 kJ/mol)
 Ca
(2251 kJ/mol)
S
Periodic Trends in Ionization Energies
 What
trends do we observe in the
ionization energies on the
periodic table?
Periodic Trends in Ionization Energies
I
increases with increasing atomic
number as we move left to right
within a period
 I decreases with increasing atomic
number as we move top to bottom
within a group
Periodic Trends in Ionization Energies
metals generally have low
ionization energies compared
with the nonmetals
 Why?
 Why are the values of I so high
for the group 8A elements?
 The
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