Group 2 – The Alkaline Earth Metals

The alkaline earth elements are in Group 2 of the Periodic Table.  In this experiment Be, Mg, Ca, Ba, and Sr will be studied.  All of the alkaline earth metals are M2+ cations (Mg2+, Ca2+, etc.) when they combine with nonmetals in ionic compounds and when they are in aqueous solution.  The reactivity of the cations of beryllium, barium, calcium, magnesium, and strontium will be examined.  The metal cations will be reacted with water.  The information will be used to rank the reactivity of the metal cations.

If a solution containing one of these cations is mixed with a solution containing an anion, the alkaline earth salt will precipitate if the compound containing those two ions is insoluble.  The anions used for testing the alkaline earth cations in this experiment is OH

M(s)  +  H2O(l)  ¾®  M(OH)2(s)  +  H2(g)

The solubilities of the compounds of the alkaline earth cations and the anions show a smooth trend consistent with the order of the cations in the Periodic Table.  That is, as we go from one end of the alkaline earth family to the other, the solubilities of the hydroxide salts either gradually increase or decrease.  By determining the solubility trends in this experiment, the order of the alkaline earths in the Periodic Table will be able to be confirmed.

Pre-Lab Assignment

As preparation for this experiment, do the following:

®  Open the prelab folder on Blackboard for this experiment and follow the instructions to prepare for this experiment.

®  Watch the video in the folder.  Use to fill in the data sheet and answer the questions.

Procedure adapted from Slowinski, et al, Chemical Principles in the Laboratory.

Periodic Trends in Group II

Report Sheet

Name:  _____________________________  Section:  _________

Instructor:  ____________________________  Date:  __________

Determine the Reactivity of Alkaline Earth Salts

Table 1 – Observations of reactivity of Alkaline Earth Salts

Metal

Describe the reaction with water.

Be

Mg

Ca

Sr

Ba

Order of reactivity from most reactive to least reactive:

Is the data consistent with the order of the Group 2 elements on the Periodic Table?