VI-1 Chem 2115 Experiment # 6 PERIODIC RELATIONSHIPS

charged). Thus electrons will be attracted more strongly and in metals electrons will be lost with more difficulty
than elements lower in each column. Conversely, for non-metals, which gain electrons to from ions, the elements
near the top of the group will be more active since fewer electrons screen the positive nucleus. This theoretical
prediction can be used to understand and explain the experimentally observed behavior.
Trends in the behavior of elements in each group are governed by the preference to have a complete outer shell.
Elements closer to complete shells tend to be more reactive than elements with electron configurations farther from
completion. The noble gas elements, which are generally unreactive, all have complete electron shells.
This experiment begins with observations of the reactivity of some metals and simple oxides (to gain insight into
trends). It then focuses on the halogen family, showing the behavior of three of these elements plus their salts and
solutions in water and hexane. Reactions between them are used to illustrate trends and to permit identification of
unknown samples.
I. Reactivity of Metals
The reactivity of Na, Li, and K from Group IA, of Mg and Ca from Group IIA, and of Al from Group IIIA
will be compared by observing some of their reactions with water and hydrochloric acid. From the
observations, comparisons between Groups and within Groups can be made.
II. Halogens
The properties of chlorine (Cl2), bromine (Br2) and iodine (I2) will be observed. Chlorine is a greenish gas
at room temperature and is commonly used in the laboratory. Aqueous solutions of chlorine will be used to
illustrate some of the properties of chlorine. Bromine will be observed in a closed tube. Iodine will be
sublimed (converted directly from the solid to the gaseous phase) and recrystallized to study its behavior.
Solutions of each of these elements in water and in hexane will be examined.
III. Halide Salts
Halide salts are compounds formed from metals and halogen elements. The potassium halide salts will be
studied by comparing their colors, solubilities, and reactivities, both alone and in combination with water,
hexane, and aqueous solutions of chlorine, bromine, and iodine.
Halide ions are formed when neutral halogen molecules are reduced (gain electrons from some other
species, which loses them). Halide ions may lose their electrons to a more active halogen. In this
experiment, chloride (Cl - ), bromide (Br - ), and iodide (I - ) ions will be combined with aqueous (water)
solutions of Cl2, Br2, and I2 molecules to observe when these reactions will occur. Hexane will be added to
provide evidence of reaction, since the halogen molecule which remains after reaction (or lack of reaction)
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