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Unformatted text preview: Section 12.16 Alkali Metals (Know the Facts Professor Friesner)- Group all the way to the Left: Alkali Metals - First Group in from the left: Alkaline Earth Metals - Group all the way to the right: Noble Gases - First group in from the left: Halogens - Block in the middle of the periodic Table: Transition metals Essentially look at figure 12.39 in your book and know it. Do not waste time memorizing which elements are classified as metalloids - Metals generally lose electrons to make cations, Non-metals are generally electron acceptors - You do not need to know the numbers in table 12.9, but you do need to know the trends. - As you go down the alkali metals from lithium to cesium, the melting point, boiling point, ionization energy, and hydration energy all decrease - As you go down the alkali metals from lithium to cesium, the density, atomic radius, and ionic radius (of the +1 ions) all increase - The hydration energy is the energy released when water molecules attach to a metal in the +1 oxidation state (in other words M + where M is the metal). For Li + , Na + , and K + this energy is < 0 which means it is exothermic. - Lithium has the most negative hydration energy meaning it gives off the most energy when water attaches to Li + , as compared to Na or K. The reason for this is that Li + ion is the smallest ion among Li, Na, and K so the charge to size ratio is largest (i.e. the charge is most concentrated) and subsequently the polar water molecules are more strongly attracted to it. - Because Lithium has the most negative hydration energy we might expect it to react more violently with water, this is not the case. When Na and K react with water, the heat is enough to melt the Na and K so that more Na and K atoms are exposed to the water and we get a violent reaction. - Lithium solid has a higher melting point so the heat generated upon hydration is not enough to melt the lithium. This means that although the reaction of lithium with water is more exothermic than Na or K, it is a slower reaction and thus not as violent. So if you tossed 1 mole of Na(s) and 1 mole of Li(s) in water, the lithium would ultimately give off more energy but the sodium would give off the energy really quickly and violently. C HAPTER 13 STUDY GUIDE Electron affinity This is the energy associated with the addition of an electron to an atom in the gas phase. The electron affinity goes up, becomes more negative, as you travel from bottom to top and left to right within the periodic table with some exceptions. Consider nitrogen, which has a less negative affinity than either carbon or oxygen. Ionization energy This is the energy associated with the removal of an electron to an atom in the gas phase. The ionization energy goes up, becomes more positive, as you travel from bottom to top and left to right within the periodic table with some exceptions. Consider again nitrogen, which has higher ionization energy than carbon or oxygen....
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This note was uploaded on 03/04/2010 for the course CHEM 1401 taught by Professor Friesner during the Spring '10 term at Columbia.
- Spring '10
- Noble Gases