The Periodic Table of the Elements

In the mid-1800s, scientists found that when all= the known elements were arranged in a sequence of increasing atomic mass and according to their properties, the properties of the elements repeated in a regular, or periodic, manner. In this lab, you will investigate some representative elements in several of the vertical groups or families of the periodic table and classify the elements as metals, nonmetals, or metalloid= s. In general, metals are solids at room temperature. They have a metallic lus= ter and are malleable. Metals conduct electricity, and many react with acids. On the other hand, nonmetals can be either solid, liquid, or gas at room temperature. If a nonmetal is a solid, it’s likely to be brittle rath= er than malleable. Nonmetals do not conduct electricity and do not react with acids. Metalloids combine some of the characteristics of both metals and nonmetals= .

Your experimental data will allow you to classif= y some elements as metals, nonmetals, or metalloids and to determine general trend= s in metallic and nonmetallic characteristics within the periodic table.

PROBLEM

What is the pattern of metallic and nonmetallic properties of the elements in the periodic table?

OBJECTIVES

• Observe the properties of samples of the elements, including metals, nonmet= als, and metalloids.

• Classify the elements as metals, nonmetals, or metalloids.=

• Analyze your results to discover trends in the properties of the elements in the periodic table.

HYPOTHESIS:<= /p>

MATERIALS

stoppered test tubes containing small samples of carbon, nitrogen, oxygen, magnesium, aluminum, silicon, red phosphorus, sulfur, chlorine, calcium, selenium, tin, iodine, and lead

plastic dishes containing samples of carbon, magnesium, aluminum, silicon, sulfur, and tin <= /span>

micro-conductivity apparatus

1M HCl <= /o:p>

test tubes (6)

test-tube rack

10-mL graduated cylinder

spatula

small hammer

glass marking pencil

SAFETY PRECAUTIONS

Wear goggles and an apron at all times. Be cauti= ous when using 1M HCl. If any of the acid to= uches your skin or eyes, immediately rinse with water and notify your teacher. Ne= ver test chemicals by tasting.

PROCEDURE

1. Use the table to record your data and observations.

2. Observe and record the appearance of each of the elements. Your description should include physical state, color, and any ot= her observable characteristics such as luster. Don’t open any of the test tubes.

3. Remove a small sample of each of the six element= s in the dishes. Place the samples on a hard surface designated by your teacher.= Gently tap each of the elements with a small hammer. An element is malleable if it flattens when tapped.

It is brittle if it shatters when tapped. Record= your observations in the data table.

4. Test the conductivity of each of the six element= s in the dishes by touching the electrodes of the micro-conductivity apparatus t= o a piece of the element. If the bulb lights, you have evidence of conductivity. Record your observations in the data table. Wash the electrodes with water,= and dry between testing each element. Wash the electrodes with water, and dry between testing each element.

5. Use a graduated cylinder to measure 5 mL of water into each of the six test tubes.

6. Label each test tube with the symbol of one of t= he elements.

7. Using a spatula, put a small sample of each of t= he six elements (a 1-cm length of ribbon or 0.1-0.2 g of solid) into a test tube labeled with the symbol of the element.

8. Add approximately 5 mL of 1M HCl to each of the test tubes and observe t= he elements for at least one minute. Evidence of reaction is the formation of bubbles of hydrogen on the element. Record your observations in the data table.=

DATA AND OBSERVATIONS

ANALYZE AND CONCLUDE

1. Interpreting Data Which elements displayed the general characteristics of metals?

2. Interpreting Data Which elements displayed the general characteristics of nonmetals?<= o:p>

3. Interpreting Data Which elements displayed a mixture of metallic and nonmetallic char= acteristics?

APPLY AND ASSESS

1. Use the boxes provided on below to construct an = abbreviated periodic table. Label the squares across the top from left to right as Grou= ps 1 and 2 and 13-17. Label the squares down the side as Periods 2-6. Write the appropriate atomic number and element symbol in each of the squares. Based = upon your answers to the Analyze and Conclude questions, write your classificati= on of metal, nonmetal, or metalloid for each of the elements you observed and/= or tested.

2. Do the metallic characteristics of the elements = across a period seem to increase from left to right or from right to left?

3. Do the metallic characteristics of the elements = in a group seem to increase from top to bottom or from bottom to top?=

4. The metalloids indicate the approximate border b= etween metals and nonmetals on the periodic table. Based upon your observations, d= raw a dark line along this border.