Periodicity

Goal: To organize unknown elements based on observed properties and develop a periodic table.

The elements are organized in the periodic table based on observed properties and trends. For example, moving across the table left to right, the elements in a row

become less metallic, the atomic radius decreases and the ionization energy increases. In this experiment, you will test 12 elements for reactions with water, with

0.1 M Na3PO4 and with 6 M HCl. Based on the results and the information given below, you will construct a periodic table for the 12 elements.

Element	A	B	C	D	E	F	G	H	I	J	K	L
Conductivity	+	+	+	+	+	+	+	+	-	+	-	+
Atomic Radius (pm)	80	170	120	120	200	140	150	140	100	130	130	130
Ionization E Kcal/mol	260	140	180	180	100	180	120	170	240	220	240	170

Experimental:

The instructor will demonstrate the first reaction with water.

Observe each of the elements and record your observations.

Test each of the remaining elements with water. Place approximately 10 mL of distilled water in a test tube. Carefully add a small spatula tipful of the element.

Observe and record the results.

For elements that reacted, obtain about 2 to 3 mL of a salt solution of the element in a test tube. Be sure the label on the salt solution matches the unknown that

reacted in the first part of the experiment. For example, if unknown A reacted with water, you will want to use unknown A salt solution for this part of the

experiment. Add 2 to 3 mL of 0.1 M Na3PO4 to the element. Observe and record the results. Salts of elements in the second column (Group II, Alkaline Earth metals) will form precipitates while those in the first column will not.

For elements that did not react with water, obtain a second small spatula tipful of the element in a test tube. Carefully add 5 mL of HCl to the test tube. Observe

and record the results. For any elements that do not react, carefully heat the test tube in a water bath under the fume hood. Observe and record the results.

Place all solutions and unreacted elements in the waste bottles. Do not throw anything down the drain.

Questions:

1.Does the appearance of the element help you classify it as a metal or nonmetal?

2.Which elements reacted with water? Were some more vigorous than others?

3.Which elements reacted with Na3PO4?

4.Which elements reacted with cold HCl? Hot HCl?

5.Based on these observations, construct a "Periodic Table" for these elements.

6.Can you identify any of the elements?