Shells Class Activity

AP Chemistry: Shells Class Activity Question: How are electrons “arranged” in an atom? 1. Describe the nature of the interaction between protons and electrons in an atom. Consider using some or all of the following terms in your description: attraction, repulsion, neutral, positive, negative, charge, distance, nucleus, force, energy, Coulomb’s Law. 2. Compare the relative energy necessary to separate positive and negative electrical charges in the following situations. Compare a and b, then compare a and c. 3. Consider the following diagram: a. How many electrons do you see in the picture? ______ How many protons? ______ b. Which of these electrons is the easiest to remove? (i.e., which requires the least amount of energy to ionize?) c. Explain your response in b. d. How does the energy required to remove the outermost electron in 3 compare to 2a? to 2c? The first ionization energy is defined as the minimum energy that must be added to a neutral atom, in the gas phase, to remove an + – electron from that atom. This definition can be represented in the following chemical equation: energy + A(g)  A (g) + 1e 3. + – In the ionization equation above, which is at lower energy? A(g) or A (g) and 1e ? + – Which is at higher energy? A(g) or A (g) and 1e ? Explain. 4. Explain why energy is required to remove the electron in a neutral atom. 5. The value of the first ionization energy for hydrogen is 1312 kJ/mol. In Figure 1 below, use a short horizontal line to indicate the + energy of H(g) (reactant) and a short horizontal line to indicate the energy of H (g) + 1e (product). (NOTE: Be sure to consider your responses to Q4 and Q5 above.) Figure 1 6. What does the difference in energy in the lines in your diagram above represent? 7. The values for the first ionization energy for a hydrogen and helium atom are provided in the table below. Atom Ionization energy (kJ/mol) H He 1312 2373 Li Based on comparisons you made in Question 2, how would you explain the difference in the values for the first ionization energy for hydrogen and helium? How does your explanation account for the relative charge on hydrogen and helium and the distance of the electron(s) from the nucleus? 8. In the energy diagram below draw a horizontal line to represent the first ionization energy for hydrogen and the first ionization energy for helium. Figure 2 9. How does your diagram illustrate the relative ease with which an electron can be removed from hydrogen and from helium? Which one is easier to remove? 10. Predict an approximate value for the first ionization energy for lithium. Do not add your prediction to Figure 2 just yet. Justify your prediction based on Question 2. 11. The value of the first ionization energy of lithium is 520 kJ/mol. Add this value for lithium to Figure 2 above. Based on comparisons you made in Question 2, how would you explain the ionization energy for lithium compared to the ionization energy for helium? Compared to hydrogen? 12. Predict the relative value of the energy necessary to remove a second electron (called the second ionization energy) from lithium. Support your prediction with an explanation. 13. Based on the first ionization energies for hydrogen, helium, and lithium that you represented in Figure 2, what can you say about the distance of the electrons from their respective nuclei in these three atoms? 14. The first ionization energies for selected elements from the second period of the periodic table follow: Atom 3Li 4Be 6C 7N 9F 10Ne Ionization Energy (kJ/mol) 520 899 1086 1302 1681 2081 Explain the trend in ionization energies in terms of the relative location of the electrons and the charge of the nucleus. 15. The first ionization energy for the element sodium is given in the following table. Predict the other values for the first ionization energy for the selected third period elements: Atom 11Na Ionization Energy (kJ/mol) 495 How did you arrive at your predictions? 12Mg 14Si 15P 17Cl 18Ar 16. The table below contains the ionization energy for each of the 18 electrons in an argon atom. The graph of this data is shown in Figure 3. Electron Energies for the Argon Atom 0 -50000 -100000 -150000 Energy (kJ/mol) electron removed 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th Ionization Energy (kJ/mol) 1520.6 2665.8 3931 5771 7238 8781 11995 13842 40760 46186 52002 59653 66198 72918 82472 88576 397604 427065 -200000 -250000 -300000 -350000 -400000 -450000 0 4 8 Electron 12 16 Figure 3 a. Interpret the graph in Figure 3. Put a box around the electrons that are easiest to remove. Circle the electrons that are the most difficult to remove. b. Based on your responses from the previous questions, how many ‘groups’ (levels or shells) of electrons are shown for Argon in Figure 3? c. Indicate the number of electrons in each group/level that you identified. d. On the graph in Figure 3, label the groups/levels/shells with 1, 2, 3, etc. e. An electron from which energy level requires the least amount of energy to remove? An electron from which energy level requires the largest amount of energy to remove? 17. Using the back of this sheet, describe the electron structure (location of the electrons) of the atom. Consider using some or all of the following terms in your description: nucleus, electron, energy, distance, level, proton, shell, arrangement, attraction, repulsion, positive, negative, charge, location.