Experiences

Periodic properties

Elena Margheri

Italy

Vocational School

Chemistry

Teaching in class

Direct

Periodic properties are studied in the first and in the second year of the secondary school. In the first year, we focus our attention on empirical considerations based on the reactivity of the elements, following Mendeleev approach. During the second year, we correlate the properties of each element with its electron configuration in a more theoretical approach. This approach is scarcely appreciated by the students and they hardly understand its importance in predicting reactivity and chemical-physical properties of elements and compounds.
In the second year, after a brief introduction of these properties to the class, I found useful to divide students in groups of 4-5 persons, which were involved in producing a research about the three subjects I considered simpler and helpful to introduce the chemical bond, that is:
1) ionization energies of elements with Z from 1 to 18;
2) all the 18 ionization energies of argon;
3) Linus Pauling’s life (the father of electronegativity and chemical bond).
Students had to analyse the information they found, with particular attention to measure units, trying to define them and to find the conversion factor.
At the end, one student for each group was asked to relate the results, possibly using presentation software and tables just to have a quick and less boring exposition.
The second issue of the research revealed difficult to be completed, since usually only the first 8th ionization energy values are collected in tables.
On this argument, the students had to spend more time and I had the chance to observe different behaviours and different skills among them.
Then, we compared results found in 2 different web sites: http://en.wikipedia.org/wiki/Ionization_energies_of_the_elements_(data_page) and http://www.webelements.com/argon/atoms.html.
This activity was mostly satisfactory and the following discussion allowed most of the students to comprehend electronic configuration; furthermore, it was interesting to observe that students liked very much to know everything about Pauling’s life, dealing gladly with chemical bond. This less scientific aspect moved very much also more fragile students, inspiring energy and motivation, thus confirming that emotional involvement is important in teenagers for a successful study.