Classifying Elements Using Physical Properties

Name: Date: Period:

ChemCom Unit IA Modified Lab A.10 pg. 42

Classifying Elements Using Physical Properties

Elements in periodic tables are positioned in ways that group elements with similar physical and chemical properties together. Mendeleev created his first periodic table by carefully observing the physical and chemical properties of the elements. In this lab you will try to classify eight different elements into three broad categories, metals, non-metals, and metalloids (semi-metals), based only on their physical properties.

Three physical properties; luster, conductivity, and malleability, will be analyzed for each element. Elements that display all metallic physical properties are classified as metals. Elements that display all non-metallic physical properties are classified as non-metals. Elements that have some metallic and some non-metallic properties are classified as semi-metals or metalloids.

Physical Properties: Terms and Classifications

Luster

Luster describes how light interacts with the outer layer of electrons in a substance.

●Metallic (looks like metal)

●Pearly (shiny like a pearl or bowling ball)

●Earthy (dull like dirt)

Metals always have a metallic luster. Non-metals have pearly or earthy luster.

Conductivity

Conductivity describes how easily electrons can be pushed from one atom to the next.

●Non-Conductor: The electrons in Non-metals can’t be pushed between atoms so they are non-conductors and do not conduct electricity.

●Conductor: The electrons in metals can move between atoms so metals conduct electricity and are considered conductors.

An Ohm meter can be used to measure how hard it is for electrons to move by measuring the resistance in units called Ohms. Good conductors will have a low resistance or low number of measured Ohms.

Metals are conductors, non-metals are non-conductors.

Malleability

Malleability describes how locked in place the bonds are that hold the atoms in a substance together. Metals are held together by flexible “metallic” bonds that allow the bonds to bend and flex.

●Ductile (can be pulled into thin wires)

●Malleable (can bend or flex)

●Brittle (Fixed bonds that shatter when stressed)

Metals are ductile or malleable, non-metals are brittle.

Procedure:

Before beginning the lab, fill out the predicted classification column with metal, non-metal, or metalloid for each element.

Determine the conductivity of each element using an Ohm meter. Report your conductivity in Ohms. While doing the conductivity testing, describe the luster of each element using the correct luster terms from above.

Determine the malleability of each element by gently tapping small pieces of each element with the hammer provided. Describe the malleability of each element using the correct terms from above.

When your Observations are Completed,Color Code Your Data Table:

Choose one color to represent metallic properties, a different color to represent non-metallic properties. Color-code each observations you recorded in your data table as either a metallic property, or a non-metallic property.

Your final classification should be done based on your observations. Elements with ALL metallic properties should be classified as metals. Elements with ALL non-metallic properties should be classified as non-metals. Elements with a mix of metallic and non-metallic physical properties are classified as metalloids (semi-metals).

Physical Properties of Elements Lab: Data Table (Observations)

Questions: Focus on “Claims and Evidence.” Every time you answer a question you are making a “claim.” Every “claim” must be supported with specific evidence from the lab and/or text. Answer the questions below.

1. Based on the conductivity measured, which element would be the best choice to use to make electrical wire?

1. Which two physical properties do you think were important in choosing copper as the metal to coat pennies? Explain.

1. Look at the periodic table on the back cover of your textbook. One of the elements should be classified differently than our test results suggest. Which element is classified differently on the book’s periodic table?

4.Atoms are made of protons, neutrons and electrons. Which part of an atom is moving through the metal when it conducts electricity?

5.

Unit 1A Lab A.10 PRELAB

Classifying Elements Using Physical Properties

PRELAB: Using the lab handout please fill out the following chart.