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Unformatted text preview: tals: LUMO+
1, 2, 3 Shell/subshell
5p Energy Shape* *Notice that inner shells may not appear correct because of approximations and scale. Dakota State University Page 100 of 232 Experiment 8: Periodicity General Chemistry I and II Lab Manual Experiment 8: periodicity
Purpose: To observe what is meant by “periodicity” and relate periodicity to electronic
Perv: I think we ALL know a few people who fit into this category Background:
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
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.
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 Dakota State University Page 101 of 232 Experiment 8: Periodicity General Chemistry I and II Lab Manual For this part of the project, you may split this work with your lab partner and no more
than one additional group (five people maximum), but you must report the data that you
personally were responsible to obtain. Write down the information you obtained in your own lab
notebook, and don’t forget to give the URL address or reference the source from which it was
obtained. This is an on- line project, so do not use any print resources (unless they are fully
available on- line as well).
With the other people you are working with, obtain the following information:
For the first 18 elements (H through Ar), find the atomic radii, melting points, boiling
points, electronegativities, and first ionization energies. Graph this data in your lab notebooks in
accordance with the calculations section.
Part II B:
ON YOUR OWN, find the following information for the Oxide of ONE O...
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