Periodic Properties

Periodic Properties - Using Periodic Properties to Identify...

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Using Periodic Properties to Identify Group 2A Cations and Group 7A Anions Objectives The objectives of this lab are as follows: To observe the solubility properties of various ionic compounds containing alkaline earth metal cations. To observe the relative abilities of the halogens to be reduced to halides, or act as oxidizing agents. To use the above observations to identify an unknown salt consisting of an alkaline earth metal cation and a halide anion. Background Elements within a given column of the periodic table tend to have similar properties due to their similar valence electron configurations. Because of this, columns of elements are often referred to as “groups” or “families” of elements. These families include the alkali metals, alkaline earth metals, halogens, and noble gases. The physical and chemical properties of the elements within a given family tend to change gradually as one goes from one element in the column to the next. In this experiment the properties of elements in the alkaline earth metal and halogen families will be studied and this data used to identify an unknown salt consisting of an alkaline earth metal cation and a halide anion. Group 2A—The Alkaline Earth Metals The alkaline earth metals— beryllium, magnesium, calcium, strontium, barium, and radium—are all moderately reactive. Beryllium compounds are quite rare and often very poisonous and radium compounds are highly radioactive; thus, neither of these will be studied. Alkaline earth metals lose two electrons to make ions with a +2 charge and can thus be represented generically as M2+. When solutions containing these cations are mixed with solutions containing anions such as CO32-or SO42-, ionic compounds of the general form MX will precipitate if the compound MX is insoluble under the reaction conditions used, as shown in the net ionic equation below. M2+ (aq) + X2- (aq) MX (s)
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This note was uploaded on 11/16/2011 for the course CHM 2045 taught by Professor Mitchell during the Fall '07 term at University of Florida.

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Periodic Properties - Using Periodic Properties to Identify...

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