The Periodic Table

1. The Periodic Table Chapter 4

2. Reading Check Why did Mendelevplace certain elements together in the same group? Arranged elements with similar properties into groups. 4.1 Mendeleev’s Periodic Table (1869)

3. Reading Check: Why did Mendeleev leave gaps in his periodic table? ANS = He predicted that elements would later be discovered to occupy these gaps 4.1 Mendeleev’s Periodic Table (1869)

4. 4.1 Periodic Table • Why does the PT have the shape it does?

6. 4.1 Periodic Table • Elements are organized in order of increasing atomic number • Atomic mass follows the same order (in most cases)

7. 4.1 Periodic Table • Mendeleev did not know why certain elements have similar properties because he did not know about atomic theory. • But we do now! Why do properties repeat themselves? • The properties of an element are determined by it’s valence electrons.

8. 3.3 Valence Electron Anelectronthatisfoundontheoutermostshellofanatomandthatdeterminestheatom’schemicalproperties.

9. 3.3 Valence Electron An electron that is found on the outermost shell of an atom and that determines the atom’s chemical properties. The electrons that are on the inside are called core electrons Which element is this? 

10. Think about it….. How many valence electrons are in there in a sulfur atom? (first, write the electron configuration)

11. Think about it….. 1s2 2s2 2p63s2 3p4 2-8-6 How many valence electrons are in there in a sulfur atom? 6 valence electrons The rest are core electrons. How many core electrons? 10

12. 4.1 Valence electrons • How many valence electrons are there in a fluorine atom? • (first, write the electron configuration for fluorine)

13. 4.1 Valence electrons • How many valence electrons are there in a fluorine atom? • 1s22s22p5 • [He]2s22p5 • 2-7

14. 4.1 Periodic Table • A period (group/period) is a horizontal row in the periodic table  • numbered 1-7 • Corresponds to the energy level of the valence electrons

15. 4.1 Periodic Table A group is a vertical column in the periodic table ↓ Groups 1-18 See fig 3 p 119 s-block, p-block, d-block, f-block

17. Think about it….. • What is the name of the group of elements containing fluorine, chlorine, bromine and iodine? • How many valence electrons do these elements have? • What is the main characteristic of these elements? ANS= • The halogens • 7 valence electrons • High chemical reactivity

19. 4.3 Trends in the periodic table Standard Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outer energy level of atoms. Learning Target Students learn about periodic trends in atomic radius by plotting/interpreting a graph

20. Think about it…. Atoms are small……but are they all the same size? Is a carbon atom the same size as an iron atom?

21. 4.3 Trends in the PT Worksheet: Family Characteristics Part 1: Atomic Radius How is atomic radius defined? See fig 19 p. 135

22. 4.3 Trend in Atomic Radius Draw in the lines for groups 2,13,14 & 17 on your worksheet. Inference: What is your graph telling you? What is the trend in atomic radius as you read down a group in the PT? What is the trend in atomic radius as you read across a period in the PT?

23. 4.3 Atomic Radius Summary See fig 20 p. 135, fig 21 p. 136 Inference: What are these diagram telling us? How are these diagrams similar/different from the one we plotted?

24. 4.3 Trends in the PT • How does atomic radius change as you read down a group in the PT? • ANS = Atomic radius increases(increases/decreases) as you read down a group in the PT.

25. 4.3 Electron Shielding

26. 4.3 Trends in the PT • How does atomic radius change as you read across a period in the PT? • ANS = Atomic radius decreases(increases/decreases) as you read across a period in the PT.

27. 4.3 Trends in the PT Atomic radius decreases as you read across a period in the PT. COUNTERINTUITIVE  Read p. 136 ‘Atomic Radius Decreases as You Move Across a Group’

28. 4.3 Electron Shielding Read p. 136 ‘Atomic radius decreases as you move across a group’ • Factors: • Effective nuclear charge • Shielding

29. 4.3 Atomic Radius Summary fig 20 p. 135 Inference: where are the largest elements found on the PT? The smallest?

30. 4.3 Atomic Radius Summary fig 21 p. 136 Inference: what is this diagram telling us? How does this diagram differ from the one we plotted?

31. 4.3 Trends in the periodic table Standard Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outer energy level of atoms. Learning Target Students learn about periodic trends in atomic radius by plotting/interpreting a graph

32. Check For Understanding: Atomic Radius Which of the following elements has the smallest atomic radius? Magnesium Calcium Strontium Barium 2. Which of these elements has the largest atomic radius? Gallium Germanium Selenium Bromine

33. 4.3 Ions Notes: • Whenatomshaveequalnumbersofprotonsandelectronstheyareelectricallyneutral

34. 4.3 Ions • When atoms have equal numbers of protons and electrons they are electrically neutral. • Butwhenenoughenergyisadded,theattractiveforcecanbeovercome.

35. 4.3 Ions • But when enough energy is added, the attractive force can be overcome. • Whenthishappens,anelectronisremovedfromtheatom,anditbecomesapositivelychargedion

36. 4.3 Ions • When this happens, an electron is removed from the atom, and it becomes a positively charged ion. (p. 133) Positively charged ion = ‘cation’

37. IONS

38. 4.3 Ionization Energy Ionization Energy = The energy that is needed to remove an electron from an atom. Na atom  Na+ ion + electron

39. Ionization Energy (kJ/mole)

40. 4.3 Ionization energy If ionization energy is high, it is difficult (difficult/easy) to remove an electron from the atom. Ionization energy is related to chemical reactivity.

41. 4.3 Trend in ionization energy Read Family Characteristics worksheet Part 2 Draw in the lines for groups 1,13,15,17,18 on your worksheet. Inference: What is your graph telling you?

42. 4.3 Ionization Energy • Ionization Energy decreases (increases or decreases)as you read down a group in the PT. • Ionization Energy increases (increases/decreases) as you read across a period in the PT

43. Think about it….. • In the Brainiac alkali metals video clip, which group 1 element was the most reactive when put into water? ANS = Those at the bottom Rb & Cs

44. 4.3 Ionization Energy Read p. 133 ‘Ionization Energy Decreases As You Move Down a Group’

45. 4.3 Electron Shielding

46. 4.3 Effective Nuclear Charge Read Ionization Energy Increases as you Move Across a Period p. 134

47. 4.3 Effective Nuclear Charge Why is the ionization energy for chlorine greater than that for magnesium?

48. 4.3 Ionization Energy See fig 17 p. 134 Inference: which elements have the highest ionization energy? The lowest?

49. Periodic Trends What is the relationship between atomic radius and ionization energy? An atom with a small atomic radius has a high (high/low) ionization energy. e.g. Fluorine

50. Periodic Trends What is the relationship between atomic radius and ionization energy? An atom with a large atomic radius has a low (high/low) ionization energy. e.g. Cesium