Practice Extra Sheet on Electron Energy Diagrams Many of you have expressed concern over reading electron energy diagrams so this is to provide a little more explanation and to give you more practice on this topic. Electron energy diagrams are merely a visual representation of the allowed energy levels around a nucleus and of the electrons contained in them. The y-axis is always increasing energy. Sometimes the allowed energy levels are labeled with their n and l values but not always.
3s energy 2p 2s
Electron diagrams for different atoms/ions can be drawn side-by-side to allow comparison of the energy levels. This can also allow you to determine which atom/ion has a higher/lower electronegativity, a higher/lower ionization energy, which is more likely to become an anion and which is more likely to become a cation.
energy
A
B
C
Ionization Energy: Electrons contained in lower energy levels are very stable (happy) and are difficult to remove. Conversely, electrons contained in higher energy levels are less stable (less happy) and are easier to remove. For example, the 2p electrons above are easier to remove than the 2s electrons. So, for the atoms above (A,B and C): To chose the one that will have the lowest ionization energy, you must find the one with its highest energy electron at the highest energy. This would be A. To chose the one that will have the highest ionization energy, you must find the one with its highest energy electron at the lowest energy. This would be C. Ionization energy will also tell you which is most likely to be a cation. So, the one with the highest ionization energy is the least likely to become a cation (hardest to remove an electron from). And, the one with the lowest ionization energy is the most likely to become a cation (easiest to remove an electron from). A is most likely become to a cation and C is the least likely to become a cation. Electronegativity: Empty spaces in lower energy levels are the most likely to be filled first. And, conversely, empty spaces in higher energy levels are less likely to be filled until all lower lying orbitals are filled. So, for the atoms above (A, B and C): To chose the one that will have the highest electronegativity, you must find the one with the lowest energy empty space. This would be A. To chose the one that will have the lowest electronegativity, you must find the one with the highest energy empty space. This would be B. Electronegativity will also tell you which one is the most likely to become an anion. The one with the highest electronegativity is the most likely to become an anion (easiest to add an electron to). And, the one with the lowest electronegativity is the least likely to come an anion (hardest to add an electron to). A is most likely to become an anion and B is the least likely to become an anion.
Practice:
energy
A
B
C
a) Which atom would have the highest electronegativity? b) Which atom would have the lowest electronegativity?
_________ _________
c) Which atom would have the highest ionization energy? _________ d) Which atom would have the lowest ionization energy? e) Which atom is most likely to become an anion? f) Which atom is least likely to become an anion? g) Which atom is most likely to become a cation? h) Which atom is least likely to become a cation? _________ _________ _________ _________ _________
3s energy 2p 2s
i) Which electron will be the easiest to remove? j) Which electron will be the hardest to remove?
2p or 2s 2p or 2s
_______ _______ _______
k) Which energy level will take on an extra electron first? 3s or 2p
Answers: a) B, b) A, c) B, d) C, e) B, f) A, g) C, h) B, i) 2p, j) 2s, k) 2p