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)!