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September 3 Notes

September 3 Notes - Chemistry 151 September 3 2008...

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Chemistry 151 September 3, 2008 Avogadro’s Number: 6.0221420•10 23 Avogadro’s Number is equal to the number of atoms in 12 g (exactly) of 12 6 C. We call 6.022•10 23 particles of something one mole (abrv. mol) of that substance. One mole of an elemental substance has a mass equal to that element’s average atomic mass expressed in grams. Mass Mole number of particle conversions 1 amu=1.66054x10 -24 g 1 g = 6.022x10 23 amu 1 mol = 6.022x10 23 particles To calculate the average atomic weight of an element, take the weighted average. o Multiply weight by percent abundance. The Periodic Table Dmitri Mendeleev (1834-1907) Organizing scheme for the elements. o Based on increasing mass. Also noticed elements in regular intervals share similar properties. o Vertical columns = groups We now know that rather than by increasing mass, elements should be ordered on increasing atomic number (number of protons in the nucleus). Organization 1. Alkali Metals 2. Alkaline Earth Metals 3. Transition Metals 4. Halogens 5. Noble Gases (Inert Gases) QuickTimeª and a decompressor are needed to see this picture.
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