Catalyst1. 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, Ca6. Order the following from largest to smallest atomic radius: O, Po, S
- Answer: O, S, Po7. 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 radius2. 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)!