Metal, Nonmetal, or Metalloid
Properties of Selected ElementsIntroduction:The sections of the periodic table reflect the electron configurations of the elements and the sublevels occupied by the electrons. It is the electron configuration of the atom that determines its chemical reactivity. An element’s position in the periodic table is directly related to the size of the element’s atoms. The size of the atoms increases as you go down each column and decreases as you go from left to right. Elements whose atoms have identical arrangements of electrons in their highest energy levels have similar properties and make up a family of elements in the periodic table (vertical columns). Elements on the Periodic Table are grouped into metals, nonmetals and metalloids based on some key physical and chemical properties.Elements combine chemically to form compounds. Bulk properties (physical and chemical) are determined by microscopic structures and interactions between atoms, ions and molecules. Common household substances span the whole range of materials from ionic compounds to molecular compounds, and to elements.Purpose:Students will investigate and determine the physical and chemical properties of selected elements and common household chemicals to further students’ understanding of relationships between microscopic structures/interactions and bulk properties.Materials / Equipment:AluminumCarbonSiliconSulfurMagnesiumZincCopperNail24 cell well plateForcepsConductivity tester1.0 M HCl, 5 mL0.1 M CuCl2, 5 mLWell-plate grid paperSpatulaKimwipesDistilled water400-mL beaker as waste jarSafety:Always wear safety glasses and apron in the chemistry lab.Never eat or drink in the chemistry lab.Hydrochloric acid solution is corrosive to eyes and skin.Cupric chloride solution is toxic if ingested.Avoid contact of all chemicals with eyes and all body tissues.Pre-lab questions:What is an element?What are the general features of the Periodic Table of Elements?Draw the flow chart for classification of properties.What is a metal?What is a nonmetal?What is a metalloid?What are required for any material to conduct electricity?What is brittleness?What is malleability?Procedure:Part A – Physical PropertiesBulk samples are gathered on one bench. Data on physical properties should be collected mainly from the bulk samples. Groups should be rotating the elements and work collaboratively.Observe and record the color of each element in the Data Table. Is the sample silver, gray, colored, etc…? Be very specific in recording observations.Observe and record the luster of each element in the Data Table. Is the sample lustrous and shiny, slightly shiny, dull?Record any other physical properties that are observed about each element in the Data Table. Be specific in the observations. What form is the sample in? Is the sample crystalline, flaky, rough, smooth, flat and plate-like, rocky, in strips? Is there any odor or are any vapors given off? (Note: Avoid breathing any vapors directly. Instead of smelling a sample directly, waft the vapors from the sample toward your nose.)Determine whether each element is malleable or brittle. To do this, position a nail on the sample and gently tap the nail with a hard, solid object (hammer, piece of wood, small book). A material is malleable if it flattens or bends without shattering. A sample is brittle if it shatters or cracks into pieces when struck. Record your results in the Data Table.Use the conductivity apparatus to test the conductivity of each sample. Touch both electrodes to the element being tested. Make sure both electrodes make solid contacts with the sample and are not touching each other. Pay close attention to the relative intensity of the light. Record accordingly.Part B – Chemical PropertiesTake a clean well plate. Note the well plate is labelled rows A-D and cell 1-6. Each micro-well can be identified with a combination of the row letter and cell number. For example micro-well B3 is located on row B and cell 3. Use the forceps or metal spatula to place elements from sample vials in the well plate. Carefully record micro-plate designations in data table. For each element, transfer small amount into two separate wells. Total number of samples is 14. 7 elements for each chemical in Steps 2 and 3.Obtain one pipet full of HCl Determine the reactivity with acid of each sample by adding 10 drops of 3 M HCl to one well of each sample—a total of 7 wells will have the acid in them.Obtain one pipet full of CuCl2. Determine the reactivity with cupric chloride solution of each sample by adding 10 drops of CuCl2 to the remaining wells. Observe and record the results in the Data Table.Evidence for a chemical reaction may be the formation of gas bubble and/or discoloration on the surface of the element. Some reactions may be slow to start—be patient. Observe and record results in the Data Table.After allowing the samples to react (about 5 minutes) carefully decant the HCl off the samples with the pipet and transfer to the small waste beaker at your station. Decant the CuCl2 into another waste beaker. Empty the solid samples into the trash, but do NOT try to rinse the well plates! This is tricky to do without splattering water everywhere—just let your teacher do it!Post-lab questions:Review the data gathered for the seven elements. Sort the seven elements into groups, based on similarities and differences in their physical and chemical properties. Using this information plus information from your book, classify each group as metal, nonmetal, or metalloid.Are there any inconsistencies within the groups you made? Do any elements seem to have properties of both groups? Which? Explain.Look at the location on the periodic table of each of the eight elements tested in this lab. How do the properties of these elements compare to their general position on the periodic table? Make generalizations about the position of the metals, nonmetals, and metalloids on the periodic table.Predict the physical and chemical properties of the following elements which were not tested in this lab—selenium, calcium, and cobalt.Extension Questions/Activities:Given the following melting point data, are there any generalizations you can make about the melting points of metals versus nonmetals? Are there any exceptions? Explain.Aluminum660?CCarbon3652?CCopper1063?CMagnesium649?CSilicon1410?CSulfur 113?CZinc420?ElementChemical SymbolColorLusterOther Physical PropertiesResult of TappingReaction with AcidReactions with CuCl2ConductivityAluminumCarbonCopperMagnesiumSiliconSulfurZincProperties of Selected ElementsData Table ................
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