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CHEM 1&2 Lab Manual & worksheets pg 101

CHEM 1&2 Lab Manual & worksheets pg 101 -...

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Experiment 8: Periodicity General Chemistry I and II Lab Manual Dakota State University Page 101 of 232 Experiment 8: periodicity Purpose: To observe what is meant by “periodicity” and relate periodicity to electronic configuration Perv: I think we ALL know a few people who fit into this category Background: None Introduction: In 1869, Russian Scientist Dmitri Mendeleyev was busy considering chemical and physical properties of the known elements, and trying to find an underlying order to them. At this time, very little was known of atomic structure, and the concept of atomic number had not yet been proposed. However, a table of atomic masses were published by Stanislao Canizzaro, which Dmitri used to arrange the elements. Then, he noticed an odd thing; if he arranged the lists of elements in a table, based on atomic masses, the properties of the elements in any given column were similar to one another. Such became his “Law of Periodicity”; if you arrange elements according to atomic mass, the chemical and physical
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Unformatted text preview: properties of these elements will repeat in a periodic fashion. Now we understand his error; the elements are not arranged according to atomic mass, but rather according to atomic number. Careful examination of the periodic chart will show that there are only a handful of pairs of elements that are in their incorrect spots if you arrange the table according to atomic mass, however, so Mendeleyev’s creation was adopted and exists even today as the basic form of the periodic chart. Our purposes today are two-fold: (1) we wish to elucidate several of the trends of the periodic chart, and (2) we wish to learn of some of the on-line tools available to the chemist. Experimental Methods: Part I: On-Line Tools You will be given a presentation of current on-line resources available to chemists. In your lab manual , take note of these URL addresses, and the specific role of each site (a.k.a. the type of information each web site provides). Part II A: Periodicity...
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