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First Ionization Energy. Amy Li, Sennett Yang, Robert Liu, Josh Mukerjee. Definition of Periodic Property. The energy required to remove the highest-energy electron from a gaseous atom The energy that accompanies the reaction X (g) X + (g) + e - Denoted by I 1.
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First Ionization Energy Amy Li, Sennett Yang, Robert Liu, Josh Mukerjee
Definition of Periodic Property • The energy required to remove the highest-energy electron from a gaseous atom • The energy that accompanies the reaction X (g) X+ (g) + e- • Denoted by I 1
Description of and Reasons for Trend • 1st ionization energy is less than 2nd ionization energy • After 1st ionization, the +1 positive charge binds remaining electrons more tightly • Core electrons are closer and more tightly bound to the nucleus than valence electrons
Description of and Reasons for Trend • From left to right across a period, I 1increases • More protons = more attraction between electrons and nucleus given incomplete shielding • From top to bottom down a group, I 1decreases • Orbital size increases = electron farther away from nucleus = less attraction
Factors Affecting 1st Ionization Energy Size • Charge of Nucleus • Distance of Electrons from Nucleus • Number of Electrons Between Outer Electrons and Nucleus • Paired or Single Electron in Orbital
Description of and Reasons for Anomalies • I 1decreases suddenly from one element to the next in a period • For instance, I 1(Nitrogen) > I 1(Oxygen) • Due to electron repulsions • Nitrogen Oxygen = fills the first already-half-occupied 2p orbital = electron repulsion • Electron repulsion leads to less attraction to the nucleus