Catalyst
1. Order the following elements from smallest
electronegativity to largest ionization energy: Aluminum,
Silicon, Phosphorous.
2. Why does Germanium have a higher ionization energy than
lead? (Don’t say, “because it’s higher!”)
3. Why does silicon have a lower ionization energy than
phosphorous? (Don’t say, “because it’s more right!”)
End
Lecture 1.7 – Electronegativity and
Atomic Radius
Today’s Learning Targets
• 1.8 – I can define electronegativity and explain
how it relates to the charge of the nucleus and
the electron. Furthermore, I can explain how this
trend changes as you move throughout the
Periodic Table.
• 1.9 – I can define atomic/ionic radius and explain
how it relates to the charge of the nucleus and
the electron. Furthermore, I can explain how this
trend changes as you move throughout the
Periodic Table.
Review - Nuclear Attraction
• The negatively charged electrons are
attracted towards the positively charged
nucleus.
• The more the electron “feels” the nucleus.
The tighter it is held
Electronegativity
• Electronegativity is the measure of the ability of an
atom to attract electrons.
Electronegativity Trends
• As you go down a group, the electronegativity of
an element decreases.
• As you go across a period, the electronegativity of
an element increases.
Why Electronegativity Decreases Down a Group
• As you go down a group more orbits are added.
• Electron Shielding – Valence electrons become
shielded from the positively charged nucleus as
you add more orbits.
• Electroneg. decreases because there is a
decreased ability of the nucleus to attract
electrons because of larger distance.
Why Electronegativity Increases Across a Period
• As you move across a period you add more
protons and electrons within the same orbit.
• The larger amount of protons in the nucleus and
electrons in orbit show an increased attraction.
• This leads to increased electronegativity as you
move within a period.
Class Example
• Order the elements from smallest to largest
electronegativity: oxygen, beryllium, lithium,
Table Talk
• Order the elements from largest to smallest
electronegativity: chlorine, bromine, fluorine
Stop and Jot
• Order the elements from smallest to largest
electronegativity: silicon, aluminum, sulfur
SUMMARIZE
Relay Race Problems
1. Which has a larger electronegativity: chlorine
or silicon?
2. Which has a smaller electronegativity
magnesium or calcium?
3. Put the following elements in order from
smallest electronegativity to largest: B, F, N, O.
4. Put the following elements in order from
smallest electronegativity to largest: N, As, Bi, P
.
5. Why does bromine do a worse job of attracting
electrons than fluorine?
5 MINUTE BREAK
Tug of War
Justify – TPS
• Explain why there was a difference between
the nucleus and electron groups ability to win
the battle in the 3 different scenarios.
Atomic Radius
• Atomic Radius – The distance from the center of
the nucleus to the outermost edge of the
electron cloud
Outer edge of
electron cloud
Nucleus
Atomic Radius Trends
• Atomic radius increases as you go down a group on
the Periodic Table.
• Atomic radius decreases as you go across a period on
the Periodic Table
Why Atomic Radius Increases Down a
Group
• As you add more electron shells to an element, the
element becomes “bulkier”.
• This means that as you go down a group, more orbits
are added, so the radius becomes bigger.
Why Atomic Radius Decreases Across a
Period
• As you move across a period, more protons are
added to the nucleus.
• Also, more electrons are added within the same
orbit.
• This means there is a larger positive and negative
charge, which results in a higher attraction and a
decrease in the radius.
SUMMARIZE
You Be the Scientist!
• Take out the handout “Identify the Trend –
Electronegativity and the Periodic Table”
• With your table complete all the questions.
Relay Races
• Line up with your group at the poster
with the assigned number.
• One person at a time will answer the
projected question on the paper.
• You will go to the end of the line
after answering the question.
• You must cycle through all group
members before you answer another
question.
• You should be doing all the problems
even if it is not your turn.
Pick a Side
• I am going to project up numerous statements
• You must decide whether you agree or
disagree.
• Be prepared to defend your response!
Pick a Side Questions
1. Atomic radius is the distance from the center
of the nucleus to the first electron orbit.
2. Atomic radius increases across a period and
down a group.
3. Atomic radius decreases down a group
because you are adding more electron orbits.
4. Atomic radius decreases across a period
because there are less electrons in the same
orbit.
Pick a Side Questions (cont.)
5. Order the following from largest to smallest
atomic radius: Ca, Se, Ni
- Answer: Se, Ni, Ca
6. Order the following from largest to smallest
atomic radius: O, Po, S
- Answer: O, S, Po
7. Order the following from smallest to largest
atomic radius: Cs, F, Ga
- Answer: F, Ga, Cs
Putting it All Together!
• With your table, create a Venn
Diagram of the 3 Periodic Trends
that we have been studying
• Your Venn Diagram must include:
– The trend as you go across a period
and down a group.
– The definition of each trend
– How nuclear charge impacts each
trend
– How the number of orbits impacts
the trends
– An example, using elements, of how
it changes across a period and down
a group.
Exit Ticket
1. Define atomic radius
2. Define electronegativity.
3. Order from largest to smallest
electronegativity: Ca, Se, Ni
4. Order from smallest to largest atomic radius:
O, Po, S
Rate Yourself
• Based on the exit ticket and your current level
of understanding, rate yourself 1 – 4 on LT 1.8
and 1.9
Closing Time
• Homework 1.6 – Electronegativity and Atomic
Radius
• UNIT 1 EXAM Thursday/Friday (9/6-7/12)!