6.1. History of the Periodic Table http://www.ck12.org
6.1 History of the Periodic Table
Lesson Objectives
- Describe the history of the periodic table and the contributions of Luther Meyer, John Newlands, Dmitri
Mendeleev, Ernest Rutherford, and Henry Moseley. - Explain how the periodic table was originally organized and the inconsistencies in this first periodic table.
- Describe the relationship between atomic number and atomic mass.
- Describe our modern periodic table and how the elements are arranged.
Lesson Vocabulary
- periodic law: States that when elements are arranged in order of increasing atomic number, there is a periodic
repetition of their chemical and physical properties.
Check Your Understanding
- What is the atomic weight and atomic number of the following element?
- What do atomic number and atomic mass tell us?
Introduction
The earliest versions of the periodic table of elements emerged in the mid-1800s. At that time, there were approx-
imately 60 known elements. This table has evolved over time as additional elements have been discovered and the
known elements were arranged and categorized in slightly different ways. Today, there are 118 known elements,
which are generally arranged in the familiar form of a modern periodic table.