Claro M. Recto Information and Communication Technology High School

Doña Aurora St., Claro M. Recto, Angeles City

Telephone #(045) 887 5502

E-mail Add: cmricthsangelescity@yahoo.com Website: www.cmricthsangeles.tk

Name:

Year and Section:

Topic:

Objectives:

1. Trace the development of the Modern Periodic Table of Elements;

2. Describe the contributions of early scientists in the development of the Periodic Table of Elements; and

3. Analyze the basis of arrangement of elements in the Modern Periodic Table.

Introduction:

The periodic table is a table in which all of the known elements are listed. The table arranges the elements in order of increasing proton number to show the similarities of chemical elements. Therefore elements with structural similarities & atomic number are placed together. These elements can be placed into two different categories, metals & non-metals.

The early years of the 19th century witnessed a rapid development in chemistry. The art of distinguishing similarities and differences among atoms prompted scientists to devise a way of arranging the elements. Relationships were discerned more readily among the compounds than among the elements; thus, the classification of elements lagged many years behind the classification of compounds.

Development of the Periodic Table

It was in 1817 when Johann Wolfgang Döbereiner showed that the atomic weight of strontium lies midway between those of calcium and barium. Some years later he showed that other such “triads” exist (chlorine, bromine, and iodine and lithium, sodium, and potassium).

Another way of classifying the elements was later proposed by John Alexander Reina Newlands in 1864. He proposed that elements be classified in the order of increasing atomic weights.

As a result of an extensive correlation of the properties