Unit B Lesson 5: The Periodic Table of Elements

 Learning Targets

Big Question: Where did the Periodic Table of Elements come from?
 We use chemicals for many purposes at school, at home, and at work. It is your responsibility to make sure you know how to work with each chemical safely.

At the end of this inquiry, you should be able to answer the following questions:

  • What does the atomic number represent?
  • Who developed the first periodic table?
  • What is the difference between a family (group) and a period?
  • What do elements in a group have in common?
Page 122 to 125  in your text will help you answer these questions about the periodic table of elements.


Introduction

Before the periodic table, there was no organization of the known elements.  Some scientists organized the elements by atomic mass (mass of one atom).  Other scientists organized the elements according to how they reacted with other atoms.  It was difficult to find information on any element and to predict how it would react.

A Russian scientist named Dmitri Mendeleev developed the first table of elements in 1869:

  • He ordered the periodic table according to atomic mass.
  • He grouped elements with similar physical and chemical properties in the same column.
  • He even left blanks for elements he predicted would be found!

The main difference between the modern periodic table and Mendeleev’s periodic table is that we order it according to increasing atomic number.  The atomic number of an element indicates how many protons are in that element.


Watch

 Watch the following video to learn more about the basics of elements.

 
 

 

Try It!

Practice Worksheet: History of the Periodic Table

  1. DOWNLOAD this practice worksheet (S9_UB_S2_L5_history_periodic_table). If you prefer to use a Google Drive or PDF version of the worksheet, click here.

  2.  As you watch the video (below) "Introduction to the Periodic Table", answer the seven short-answer items on the worksheet.

  3. When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below. 

    Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
 


  1. 63 elements had been discovered.

  2. Dmitri Mendeleev

  3. Elements were in order of increasing mass.

  4. Elements were grouped vertically by similar properties.

  5. He left blank spaces predicting additional elements would be discovered.

  6. The modern periodic table is ordered in terms of increasing atomic number (or increasing number of protons).

  7. Periodic Law:  Properties change as one moves across the table, but they repeat in the next row.