2. Pretest time! Clear desk except for pen or pencil Done? Turn it in, pick up a pink packet and read the periodic table lab

3. Periodicity The similarities and differences among elements based on their location on the periodic table

4. Dmitri Mendeleev 1834 - 1907 In 1869 he published a table of the elements organized by increasing atomic mass. The “Father of the Modern Periodic Table”

5. Elements by Discovery Year

6. Periodic Table Lab On a separate sheet of paper, create the following: Title: Purpose: Using your group, identify the purpose for this lab Data Table (observations): Observations list No numbers are necessary

7. Periodic Table Lab Safety Cover immediately (Group 1A, step 3) Razor Blade Alkali Metals and Skin Phenolphthalein **Done? Work with your group on the lab questions (they are your homework)

8. Friday 3/23

9. General Periodic Trends Atomic and ionic size Ionization energy Electronegativity With a neighbor, write down everything you know about Sodium. Then, do the same for Potassium

10. Size goes UP going down a group Size goes UP going down a group Size goes DOWN going across a period (left to right) Size goes DOWN going across a period (left to right) Size goes UP going down a group Size goes UP going down a group Size goes DOWN going across a period (left to right) Size goes DOWN going across a period (left to right) Atomic Size

11. Size decreases across a period Large Small

13. Which is Bigger? Na or K ? Na or K ? Na or Mg ? Na or Mg ? Al or I ? Al or I ?

14. Ion Sizes Does the size go up or down when losing an electron to form a cation? Does the size go up or down when losing an electron to form a cation?

15. Ion Sizes CATIONS are SMALLER than the atoms from which they come. The electron to proton ratio has changed. The size DECREASES. Li,152 pm 3e and 3p Li +, 78 pm 2e and 3 p + Forming a cation.

16. Ion Sizes Does the size go up or down when gaining an electron to form an anion?

17. Ion Sizes ANIONS are LARGER than the atoms from which they come. ANIONS are LARGER than the atoms from which they come. The electron to proton ratio has changed. The size INCREASES. Forming an anion. F, 71 pm 9e and 9p F -, 133 pm 10 e and 9 p -

18. Trends in Ion Sizes Similar to Figure 11.36 in book (pg 350)

19. Which is Bigger? Cl or Cl - ? K + or K ? Ca or Ca +2 ? I - or Br - ?

20. Mg (g) + 738 kJ ---> Mg + (g) + e- This is called the FIRST ionization energy because we removed only the OUTERMOST electron Mg + (g) + 1451 kJ ---> Mg 2+ (g) + e- This is the SECOND IE. IE = energy required to remove an electron from an atom Ionization Energy

21. Successive ionization energy

22. Explaining the trends in ionization energy

23. Trends in Ionization Energy IE increases across a period. Why? Distance from the nucleus Becoming ‘more full’ IE decreases down a group. Why? Because size increases (Shielding Effect)

24. Which has a higher 1 st ionization energy? Mg or Ca ? Al or S ? Cs or Ba ?

25. Electronegativity A measure of the ability of an atom or a molecule to attract electrons to itself. Concept proposed by Linus Pauling 1901-1994 Concept proposed by Linus Pauling 1901-1994

26. Periodic Trends: Electronegativity In a group: Atoms with fewer energy levels can attract electrons better (less shielding). So, electronegativity increases UP a group of elements. In a period: More protons, while the energy levels are the same, means atoms can better attract electrons. So, electronegativity increases RIGHT in a period of elements.

27. Electronegativity

28. Which is more electronegative? F or Cl ? Na or K ? Sn or I ?

29. How is electronegativity used? To predict the nature of the bond between two atoms Is the bond polar or nonpolar? The larger the difference, the more likely that the bond is ionic NOTE: A large difference in electronegativity does not equate with a strong bond!!!