3 for the atomic radii melting points boiling points

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Unformatted text preview: F THE 18 elements for which the oxide exists (save, of course, oxygen): Reactivity with water, LD50 , and first aid treatment. Calculations: On separate pages in your lab notebook, graph the atomic radii, melting points, boiling points, electronegativities, and first ionization energies. Make sure that each graph fills the entire page by choosing appropriate scales for the x and y- coordinates (see me if you do not know how to do this). Connect your points, but also, using different color pens, connect the points for just the individual groups (that is, Group IA, Group IIA, etc.). Use these graphs to answer the post lab questions. Periodicity Post-Lab Questions 1) For the atomic radii, melting points, boiling points, electronegativities, and first ionization energies, what is the general trend as you go across the periodic chart (left to right), neglecting “gliches”? 2) For the atomic radii, melting points, boiling points, electronegativities, and first ionization energies, what is the general trend as you go down the periodic chart (from top to bottom)? 3) For the atomic radii, melting points, boiling points, electronegativities, and first ionization energies, where are the major “jumps”? (That is, the greatest discontinuities in the graph occurs between which groups?) Dakota State University Page 102 of 232 Experiment 9: VSEPR General Chemistry I and II Lab Manual Experiment 9: VSEPR Purpose: To use the Valence Shell Electron Pair Repulsion Theory to predict molecular shapes Pink: Not just a color, but also a singer Background: See “Using HyperChem” Introduction: Sure, Quantum Theory is powerful, but sometimes, simple is better. Simple implies more insightful, more intuitive, easier to utilize, and sometimes just as good as more difficult theory. One such simple, insightful theory is the Valence Shell Electron Pair Repulsion Theory (VSEPR, often pronounced as "vesper"). VSEPR is a simple model that was developed to predict the shape of covalently bonded compounds. It turned out to be exactly "on the mark". Nowadays, we can use quantum theory to predict the same thing, by forming "bonding orbitals", which are solutions to Schroedinger's equation created by the overlap of orbitals from each atom involved in the bond. The odd thing, though, is that while quantum mechanics has verified the validity of VSEPR, it gave us no real improvement to the model. Therefore, chemists today are more likely to turn to the older, simpler VSEPR model than they are the more difficult and cumbersome quantum mechanics. VSEPR: The Premise Let's begin by looking at the premise to VSEPR. It's amazing to me how simple and intuitive it is. Basically, we begin by recognizing that we are only interested in the valence shell electrons (the outermost electrons, which is where the "VS" comes from in VSEPR, the "valence shell"). Inner shell electrons do not interact with other atoms, and therefore play no part in the shape of the molecule. Secondly, we notice that electrons exist in pairs, either as bonding electrons or non...
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