Lecture 12 - Topics for the day Administrative stuff Ionic...

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Topics for the day Administrative stuff Ionic bonds Predicting ionic compounds Covalent bonds Dipole moments Administrative stuff Exam grading questions. Email me any requests. ALEKS homework objective 1 due now (extension until 10 am today) objective 2 available, due 10 am Monday March 1st Reminder that from objective 2 onwards, your ALEKS homework % = % topics covered. No Quest homework this week. For the exam question on the electronic confguration o± silver Although two answers are true, only one explains the phenomenon. The grade is unchanged. Exam One 1 2 3
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A. only one electron can occupy a 5s orbital B. an enhanced stability is associated with flled sets oF equivalent orbitals. C. the 4d subenergy level has higher energy than the 5s subenergy level. D. the 4d subenergy level always has 10 electrons E. the magnetism measurement shows one unpaired electron The ground state electron confguration oF the silver atom is [Kr]5s 1 4d 10 instead oF [Kr]5s 2 4d 9 . The observation can be explained (theoretically) by the Fact that: Exam Q False! False! Both configurations have 1 unpaired electron. True, but doesn’t explain the observation. Cu: [Ar]4s 1 3d 10 The expected confguration would have been Cu: [Ar] 4s 2 3d 9 , but the extra stability gained For a flled subshell overcomes the Fact that the 4s orbital is lower in energy than the 3d orbitals. Similarly Ag is [Kr]5s 1 4d 10 not [Kr]5s 2 4d 9 Au is [Xe]6s 1 4F 14 5d 10 not [Xe]6s 2 4F 14 5d 9 From Lecture 9 Where were we? The electron afFnity is the change in energy when an electron adds to a gaseous atom to make an anion. The more negative an EA, the more the atom wants to be an anion. EA trends are predicted by orbital size moving down a column, and by electron confguration across a row. Metals have low ionization energies and want to be cations. They are on the leFt and center oF the periodic table. Nonmetals have negative electron aFfnities and want to be anions. They are on the right top oF the periodic table. Metalloids share properties oF both metals and nonmetals. Electronegativity tells us how well an atom attracts shared electrons. Cations are larger than their parents, and Anions are smaller than their parents. The ionic radii oF an isolectronic series decrease with atomic number. Ionic bonds Form between a metal and a nonmetal and transFer electrons. Covalent bonds share electrons between two nonmetals. 4 5 6
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As an example of an ionic bond, consider NaCl: Sodium has a low ionization energy, and is happy to lose an electron. Chlorine has a high electron afFnity, and is happy to
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This note was uploaded on 03/06/2010 for the course CHEM 52375 taught by Professor Shear during the Spring '10 term at University of Texas-Tyler.

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Lecture 12 - Topics for the day Administrative stuff Ionic...

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