Predictable trends

OBJETIVES

• To recognize the way in which elements are organized in the periodic table.

• To determine physical and chemical properties of elements within a family or a period by observing the trends.

• To determine whether the reactivity and solubility of an element increases or decreases.

• To study the families in the periodic table, especially the alkaline earth metals and the halogens.

CONCLUSIONS

Many properties of the elements tend to change in a predictable way, known as a trend, as you move across the period or down a group. Our goal with this experiment was to explore the given periodic trends. It allowed us to know how to determine physical and chemical properties within a family or a period by observing the trends. We were supposed to understand the tendencies within periods or groups: in general there is a decrease in atomic radii as you move left to right in the period. Atomic radii generally increase as you move down a group.

In the data table #1 we found elements of the same family (IIA). We observed that all the members of the families are able to react with the same reagents within a column. As we went down in a family the ph number increased. After the ph test we found that those elements are classified as bases; MgO gave a dark green color (8) and the CaO gave a light green color (10). The color magenta establish in Mg is an indicator of being a base. In the second data table the combinations between the families IA and VIIA,

In the data table #3 we found almost the same observations in the given alkaline metals Na and K: in the 1st one gas evolution, radical change of color, and in the second one we saw that the reaction had increased (atomic size increases) because it caused fire, so I think that if we were going to use an element below k the reaction would be greater than the anterior.

When we compare the reactivity in the family IA with the family IIA within the same period, we noticed that as we move to the left in the period the reactivity increases, for example: we registered in element Ca just a change in the temperature and gas evolution, while the reaction in K was so much greater, we obtained the same characteristics, and also one more, a radical change of color. The prediction of combination of barium oxide and water is that it would be a base, because the data that we obtained shows that as we go down in the family the ph # increases, so it means that certainly it's ph would be greater than 11 (Ca), and we know that the bases are in the range 8-14. Based in the experimental information we can predict:

If silver nitrate and sodium astatide were combined it would form a precipitate color white.

Error paragraph: we could've have little mistakes like in the cleaning of the essay tubes, maybe some of them could have some other substance contained on it that could not be clean by us. The quantities of a substance for the mixtures are not always the same; maybe there were one or two drops of difference between mixtures.