Catalyst1. List an element from the following groups: alkali, alkaline earth metal, transition metal, halogen, and Noble gas.2. Why do different groups have different properties?3. Label as metal, non-metal, or semimetal: sodium, silicon, neon, and cobalt.

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 Problems1. 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)!