Propriedade periodicas

Periodic Properties of the Elements
Note to the Instructor: This laboratory experiment may be split into two laboratory periods, and can be done solo as a DEMONSTRATION.

Purpose: The purpose of this lab is to observe how certain properties of elements tend toward a periodic similarity when the elements are arranged in order of increasing atomic number; to note that elements (and ions of those elements) in the same vertical column (family) of the periodic table have similar properties; to note that elements (and ions of those elements) in different families of the periodic table have fewer similarities and greater differences.

Materials: Samples of elements; description of elements; solid samples of Na and K metals for instructor performed demonstrations. Mg, Ca, and Al metals for student experiments; NaCl, KCl, MgCl2, CaCl2, AlCl3 and steel wool. Reagents include 6MHCl, 0.2M NaCl, 0.2M NaBr, 0.2M NaI, 0.2M Na3PO4, 0.2M Na2CO3, 0.1M AgNO3, 6M HN03, 1M NaOH, and 6M NaOH.

Safety: The alkali and alkaline earth metals are highly reactive. Students should take care in handling calcium and magnesium when they react with water. Wear safety glasses.

Hazardous Waste: Silver is a toxic heavy metal. The contents of all test tubes to which AgNO3 has been added should be disposed of in the heavy metal waste container, DO NOT pour it down the sink.

INTRODUCTION

The periodic table is a central tool in helping us to understand regularities in the behavior of elements and compounds. In the nineteenth century people noted similarities among various elements and tried to find a pattern of relationship among them. In 1869 Dimitri Mendeleev of Russia and Lothar Meyer of Germany independently arranged the elements in order of increasing atomic weight and noted that similarities appeared at intervals. In 1913 Henry Moseley, and English scientist, determined the nuclear charge (atomic numbers) of the elements and pointed out that the fundamental