Catalyst

1. Catalyst 1. 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

3. Lecture 1.7 – Electronegativity and Atomic Radius

4. 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.

5. 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

6. Electronegativity Electronegativity is the measure of the ability of an atom to attract electrons.

7. 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.

10. 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.

11. 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.

12. Class Example • Order the elements from smallest to largest electronegativity: oxygen, beryllium, lithium,

13. Table Talk • Order the elements from largest to smallest electronegativity: chlorine, bromine, fluorine

14. Stop and Jot • Order the elements from smallest to largest electronegativity: silicon, aluminum, sulfur

15. Summarize

16. Relay Race Problems • Which has a largerelectronegativity: chlorine or silicon? • Which has a smallerelectronegativity magnesium or calcium? • Put the following elements in order from smallest electronegativity to largest: B, F, N, O. • Put the following elements in order from smallest electronegativity to largest: N, As, Bi, P . • Why does bromine do a worse job of attracting electrons than fluorine?

17. 5 Minute Break

18. Tug of War

19. Justify – TPS • Explain why there was a difference between the nucleus and electron groups ability to win the battle in the 3 different scenarios.

20. 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

21. Atomic Radius Trends • Atomic radius increases as you go down a group on the Periodic Table. • Atomic radius decreasesas you go across a period on the Periodic Table

22. 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.

23. 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.

25. SUMMARIZE

26. You Be the Scientist! • Take out the handout “Identify the Trend – Electronegativity and the Periodic Table” • With your table complete all the questions.

27. 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.

28. 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!

29. Pick a Side Questions • Atomic radius is the distance from the center of the nucleus to the first electron orbit. • Atomic radius increases across a period and down a group. • Atomic radius decreases down a group because you are adding more electron orbits. • Atomic radius decreases across a period because there are less electrons in the same orbit.

30. 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

31. 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.

32. 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

33. Rate Yourself • Based on the exit ticket and your current level of understanding, rate yourself 1 – 4 on LT 1.8 and 1.9

35. Closing Time • Homework 1.6 – Electronegativity and Atomic Radius • UNIT 1 EXAM Thursday/Friday (9/6-7/12)!