CH 5.3 -­‐ Periodic Trends WebQuest Atomic Radius (pages 150-­‐152) Using your text, please answer the following: 1. Can the radius of an atom be measured directly? 2. In what unit is atomic radius usually measured? 3. Define Atomic Radius: Go to the following website: http://www.webelements.com/periodicity/atomic_radius_empirical/bar_chart.html 4. Look at the graph. What is on the X Axis ? 5. What is on the Y Axis (include units)? 6. The colors on the graph represent rows on the periodic table. In a complete sentence, what appears to be the trend in atomic radius as you move from left to right in a row? In a complete sentence, what appears to be the trend in atomic radius as you move down a column? 7. Using your text, please answer the following: a. What is the general trend for atomic size within a group/family from top to bottom? b. What two variables affect atomic size within a group? c. What is the general trend in atomic size from left to right within a period? 8. Use the graph to the right to answer the following: a. Determine which metal has an atomic radius of 238 pm? b. Is an atom of barium, atomic number 56, smaller or larger than an atom of cesium (Cs)? c. Which has a larger atom, helium or argon? d. Which has a larger atom, potassium or argon? Ions and Ionization Energy (pages 153-­‐156) Using your text, please answer the following: 9. What is an ion? 10. How are ions formed? 11. An ion with a positive charge is called a(n) __ 12. An ion with a negative charge is called a(n) 13. Define Ionization Energy: . Go to the following website: http://www.webelements.com/periodicity/ionisation_energy_1/graph.html 14. Look at the graph. What is on the X Axis ? 15. What is on the Y Axis (include units)? 16. The colors on the graph represent rows on the periodic table. In a complete sentence -­‐ What appears to be the trend in ionization energy as you move from left to right in a row? In a complete sentence -­‐ What appears to be the trend in ionization energy as you move down a column? 17. Now click on the word cylinders at the upper left. A new graph will appear. Click on the different versions of the data. Which graph is easiest for you to interpret? 18. Using your text, please answer the following: a. Why does ionization energy tend to decrease from top to bottom within a group? b. Why does ionization energy tend to increase as you move from left to right across a period? 19. Use the graph to the right to answer the following: a. Which element in period 2 has the lowest first ionization energy? b. Which element in period 3 has the lowest first ionization energy? c. What is the group trend for first ionization energy for noble gases and alkali metal? d. If you drew a graph for second ionization energy, which element would you have to omit? Explain Ionic Size (pages 159-­‐160) 20. Using Figure 19 on page 159 to answer the following: a. Look at Figure 19 and compare the size of the ion versus the neutral atoms. These are represented with the spheres in the picture. Neutral atom size is in the upper left and ionic size is in the lower right of each square. Describe how the size changes when an atom forms a cation and when an atom forms and anion. b. Graph Atomic Number vs. Ionic Radii. c. How do the ionic radii vary within a group of metals? e. How do the ionic radii vary within a group of nonmetals? f. Describe the shape of the portion of a graph that corresponds to one period. g. Is the trend across a period similar or different for periods 2,3,4 and 5? USE YOUR OWN GRAPH PAPER 21. Use your text to answer the following: a.
Do metallic elements gain or lose electrons? b.
What charge ions do metals tend form? c.
Do nonmetallic elements gain or lose electrons? d.
What charge ions do nonmetals tend to form? c. What happens to the radius when an atom forms a cation (loses electrons – becomes positively charged)? Why? d. What happens to the radius when an atom forms an anion (gains electrons – becomes negatively charged)? Why? Electronegativity (pages 161-­‐164) Using your text, please answer the following: 22. Define Electronegativity. 23. Why are the noble gases omitted from the chart of electronegativity on p. 161? Go to the following website: http://www.webelements.com/periodicity/electronegativity_pauling/ Scroll down to the graph, click on the different types of graphs listed on buttons at the bottom to see the various representations of differences in electronegativity. You may also click on “line graph” on the top left to view that version of the relationship. 24. Which graph helps you to best identify the trends in electronegativity? 25. In a complete sentence -­‐ What appears to be the trend in electronegativity as you move from left to right in a row? In a complete sentence -­‐ What appears to be the trend in electronegativity as you move down a column? 26. What element has the highest electronegativity? 27. What element has the lowest electronegativity? Using your text, please answer the following: 28. What is the trend for electronegativity within a group? 29. What is the trend for electronegativity within a period? Electron Affinity (p157-­‐159) (Use your textbook) 30. Define electron affinity. 31. The electron affinity for sulfur is -­‐207.7 KJ/mol. Based on sulfur’s electron configuration, why is the electron affinity negative? 32. Based on electron configuration, why is the electron affinity of chlorine more negative than sulfur? 33. Based on electron configuration, why is the electron affinity of phosphorus less negative than sulfur? 34. Based on electron configuration, why is the electron affinity of selenium less than sulfur? Summarize all trends on the chart as follows. decreases Atomic radius increases Above is an example of the summary of the atomic radius trend. Sketch an outline of the periodic table (as above) a nd summarize the trends for atomic radius, ionization energy, ionic size, electronegativity and electron affinity.