Sancho's periodic classification lesson notes for advanced level New Syllabus - senkolink.ac.tz

 

SANCHO’S PERIODIC CLASSIFICATION LESSON NOTES FOR ADVANCED LEVEL

After studying this topic, you will be able to:

♠ Explore the periodic trends of elements in the modern periodic table

(Electronegativity, ionization energy, electron affinity, atomic radius,

melting point, and metallic character)

♠ Analyse the periodic trends of elements in relation to their physical and

chemical properties

INTRODUCTION:

Before the beginning of eighteenth century, only a very few elements were known and it was

quite easy to study and remember their individual properties. In 1800, only 31 elements were

known. At present about 118 elements are known of which 94 are naturally occurring. With the

discovery of large number of elements it became difficult to study individually the properties of

these elements and their compounds. At this stage the scientists felt the need of some simple

method to facilitate the study of the properties of various elements and their compounds. After

numerous attempts the scientists were ultimately successful in arranging the elements in such a

way so that similar elements were group together and different elements were separated.

In generally, chemists have for long time looked at ways of grouping elements with similar

properties. The simplest of these has been classifying elements as either metals or non-metals.

The modern periodic table is a result of efforts of some prominent scientists who utilized their

time to learn how best they could arrange the elements based on similar physical and chemical

properties.

The arrangement of elements in such a way that the similar elements fall within same vertical

group and the dissimilar elements are separated is known as classification of elements.

The classification of elements led to the formation of periodic table. Thus,

Periodic table may be defined as the table giving arrangement of all the known elements

according to their properties so that similar elements fall within the same vertical

column and dissimilar elements are separated. Or

 

Periodic table: Is the arrangement of elements in a table form according to their atomic number

such that elements with similar properties fall under same vertical column.

Periodicity: Is a tendency of a particular property of an element to appear every after a certain

 

specific interval in a given arrangement.

 

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