Ionization Energy and Electron Affinity Ionization Energy is removing an electron Electron Affinity is adding an electron Content Objectives • SWBAT describe the trends in ionization energy based on the distance an electron is from the nucleus and the shielding affect. • SWBAT describe the trends in electron affinity basxed on the distance an electron is from the nucleus and the shielding affect. Ionization Energy Ionization Energy • Energy required to remove an electron from a ground state atom Ionization Energy of Noble Gases • Noble gases have full orbitals, so it is difficult to remove an electron from them. But, it does become easier the further away the electrons get from the nucleus. Ionization Energy of Alkali Metals • Alkali Metals only have one valence electron, so it does not take much effort to remove that one electron. • When it is removed, they achieve Noble Gas Configuration. Dips in Ionization Energy • There are dips at Group 2 and Group 15. • Group 2 is because it has a full s- orbital and thus has a bit more stability. Group 15 has a half-filled orbital. General Trends Electron Affinity • Amount of energy released when an atom adds an electron • Another way to say it is; – How much does an atom want another electron? Electron Affinity of Noble Gases • Noble Gases have no electron affinity because they already have full orbitals and will not take any more… We will ignore transition metals for now Trends in Electron Affinity • The trend is to increase as you go right across the Periodic Table because there are more protons in the nucleus to attract them… Trends in Electron Affinity • The trend is to decrease as you go down the Periodic Table because the electrons are further from the nucleus. Exceptions in Electron Affinity • Notice how the Alkaline Earth and Nitrogen Group break the trend? Why do you think that is? Remember, this is related to how much they want to add electrons. Why would the Carbon Family have more electron affinity than the Boron or Nitrogen Families? Because if Carbon added one more electron, it would have 3 electrons in the p- orbital Half-filled orbitals are more stable than other states other than completely full Exceptions in Electron Affinity • Notice how the 2nd period is lower than the 3rd? • That has to do with electron crowding. Flourine wants to add another electron, but the atom is so small that they start to repel each other within the small 2p- orbital Electron Affinity of Period Two Electron Affinity of Period Two What about this one? What is the pattern of these dips? Both have full s- orbitals This has a half filled p- orbital crowding 7 valence 6 valence Carbon Family Boron Family 4 valence 3 valence Why is Group 1 higher than Group 2? 1 valence Alkali Metals vs. Alkaline Earth Families What makes the Nitrogen Family so different? Nitrogen Family General Trends Content Objectives • SWBAT describe the trends in ionization energy based on the distance an electron is from the nucleus and the shielding affect. • SWBAT describe the trends in electron affinity basxed on the distance an electron is from the nucleus and the shielding affect.
