Page 31 - Chemistry_Form_2

Chemistry
for Secondary Schools

Chapter

Two Periodic classification

FOR ONLINE READING ONLY

Introduction

Many elements have been discovered. Therefore, studying each element individually
is challenging. The elements are better understood and managed when they are
classified. The most effective way to classify them is by using a table known as the
periodic table. In this chapter, you will learn about the development of the periodic

table, electronic configuration and element positioning in the periodic table, and
changes in physical and chemical properties across periods and down the groups.
The competencies developed will provide a foundation for studying elements and
predicting how chemicals behave and their applications in everyday life.

Think

Periodic classification is the backbone of chemistry applications.

Development of the periodic table

Task 2.1

Utilise online or any reliable resources to search the dynamic changes that led to
the development of the modern periodic table.

For a long time, chemists have used various ways of grouping elements with
similar properties. The simplest of these has been classifying elements as either
metals or non-metals. In 1866, a British chemist, John Newlands, thought of the
idea of arranging elements in order of their increasing atomic masses. Newlands
arranged the elements according to Table 2.1.

Table 2.1: Newlands’ first arrangement of elements

H Li Be B C N O F Na Mg Al Si P S Cl K Ca

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