Download What is Ionization Energy?

Catalyst
1. Complete the “Goals for the week” section
on your new Daily Work Organizer.
2. Draw the following chart in the box titled
Catalyst:
http://www.youtube.com/watch?v=eCk0lYB_8c0&feature=related
Alkali Metal
Li
Na
K
Rb
Cs
Observations
Objectives
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I can define ionization energy, atomic radius,
and electronegativity.
I can identify and explain trends in ionization
energy, atomic radius, and electronegativity.
Agenda
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Catalyst
Periodic Trends Lab
Periodic Trends Post-Lab Presentations
Exit Slip: Completed Post-Lab
Periodic Table Trends
A trend is a predictable change in a certain direction. Understanding periodic
trends allows us to make predictions about the chemical behavior of the
elements.
Periodic Trends…
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We already know:
Atomic number increases as we move down a group
and also increases as we move across a period.
Trend from metals to semimetals to nonmetals as
we move across a period from left to right.
We just learned: Reactivity of alkali metals increases
as we move down the group.
Today’s investigation is about the trends regarding:
Ionization energy
Atomic Radius
Electronegativity
Pre-Lab Notes:
1. What is Ionization Energy?
 It is the energy required to take electrons
away from an atom.
2. What is Atomic Radius?
 It is the size of the atom.
3. What is Electronegativity?
 It is how much an atom pulls electrons
that it is sharing in a chemical bond
towards its nucleus.
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Investigation Procedure
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Safety Precaution: Do NOT touch the metal
tip of the hot glue gun or the hot glue at any
time. There is a very limited supply of glue,
scissors, and straws so please use these
materials carefully.
Materials
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Straws
Scissors
Periodic table
Hot glue gun
Periodic trend data chart
Ruler
Procedure Overview
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Follow directions on your trend data to
construct your straw model. (25 min)
Determine the direction of your trend and add
this information to your model. (3 min)
Clean up work space. (3 min)
Complete the Post-Lab questions. (20 min)
Be ready to present your trend to the class.
(25 min)
Attraction and Repulsion of
Electrical Charges
+
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Particles with unlike charges
attract one another.
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+
Particles with like charges
repel one another.
+
Ionization energy
Ionization energy
decreases
Ionization energy
increases
Ionization Energy Trend:
Why?
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Decreases as you move down a periodic
table group because
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the valence electrons are farther from the nucleus
and there are more electrons in the inner energy
levels shielding the attractive charge of the
nucleus.
Increases as you move across a period
because
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The number of protons increases but the valence
electrons are in the same energy level. This
creates more nuclear force holding the electrons
in.
Ionization energy:
The amount of energy needed to remove an
electron from an atom or ion.
 Atoms that want to gain electrons have
high ionization energies.
 Atoms that want to lose electrons have
low ionization energies.
 Noble gases have the highest ionization
energy.
Atomic radius: the size of an atom
Atomic radius
increases
Atomic radius
decreases
Atomic Radius Trend: Why?
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Atomic radius increases as we move down a
group because
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Valence electrons are in a higher energy level.
Atomic radius decreases as we move across
a period from left to right because
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One more proton and one more electron are
added as we move from left to right but the
electrons stay in the same energy level. The
added protons pull harder on the electrons,
decreasing the size of the atom.
Electronegativity
Electronegativity
decreases
Electronegativity
increases
Electronegativity Trend: Why?
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Electronegativity decreases as we move
down a group because
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Valence electrons are in a higher energy level
and farther from the positively charged protons.
Electronegativity increases as we move
across a period from left to right because
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One more proton and one more electron are
added as we move from left to right but the
electrons stay in the same energy level. The
added protons pull harder on the electrons,
increasing electronegativity.
5) Electronegativity: the tendency of an atom in
a molecule to attract shared electrons to
itself.
 Elements that want to gain electrons
have high electronegativies.
 Elements that want to lose electrons
have low electronegativies.
 exception: noble gases have no
electronegativity