Ch400Ch6LN1 - Chem 400 Chapter 6 Lecture Notes Part 1 Ions...

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Chem 400 Chapter 6 Lecture Notes Part 1 Ions and their Electron Configurations, and Radii • You already learned how to write the electron configurations and the Noble Gas electron configurations for ions. • Just remember that it is the valence electrons which get removed or added to first! • So you always add to or remove from the highest energy level, or n value. • Write the electron configurations and Noble Gas electron configurations for Cl - , Ca 2+ , and Mn 2+ . • Can you see why metals tend to lose electrons and why nonmetals tend to gain electrons? • What kind of electron configuration are they trying to obtain? And how many valence s and p electrons is this? Ionic Radii • When a neutral atom of Li loses its valence 2s 1 electron, what happens to the size of the Li + cation? Is it smaller or larger than Li? • Why is it smaller (think of Z eff , the effective nuclear charge and what shell the electron is lost from)? • Likewise, if an oxygen atom gains 2 electrons to become O 2- , what about the size of the oxide anion? Is it smaller or larger and why? Ionization Energy, A Periodic Property • You know that an electron in an orbital may be promoted to a higher energy level orbital if it absorbs enough energy. • But you also know that electrons may be removed from an atom entirely. • Although it is typically the valence electrons which are removed, we can actually remove core electrons as well. • So if we put in enough energy, we can remove an electron (or more than one) entirely. • The Ionization Energy is the energy required to remove an electron from an atom (or ion) in the gaseous state. The Ionization Energy is ALWAYS positive! • The first Ionization Energy, IE 1 or E i1 , is the energy required to remove the outermost valence electron from a neutral atom.
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• The second IE, IE 2 , is the energy required to remove the second valence electron from the +1 cation. • What’s the IE 3 ? • How do IE vary down a group or across a Period? • Going down a group, you add a shell, so the valence electrons are further and further from the nucleus. As the atom gets larger, the valence electron is further away, and is loosely held. So it is easier to remove, and the IE is smaller. So IE decreases
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Ch400Ch6LN1 - Chem 400 Chapter 6 Lecture Notes Part 1 Ions...

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