■ A form of classifying elements systematically by placing elements with similar features in the same group.
■ In Periodic Table
► | The elements are arranged in order of increasing proton number. | |
► | Element with same chemical properties are placed in the same group. | |
► | The characteristic of the element and its compounds can be predicted, thus making the study of chemistry easier and more systematic. |
► | Several scientists have contributed greatly to the development of the Periodic Table in the eighteenth and nineteenth centuries. | |||||||||||||||||||
► | The following table shows the contribution of scientists in the development of the Periodic Table.
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■ Periodic Table
► | Arranged according to ascending proton numbers of the elements. | |
► | Elements with the same chemical properties are placed in the same group. | |
► | The animation below shows the Modern Periodic Table. | |
► | The animation below shows the summary of information which can be obtained from the Periodic Table. |
► | Vertical columns of the Periodic Table. | |||||||||||||
► | Each member of a group shows similar chemical properties. | |||||||||||||
► | Physical properties show a gradual change when descending the group. | |||||||||||||
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Some of the groups have special names.
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► | Horizontal rows of the Periodic Table. | |
► | The proton number increase by one across the period from left to right. | |
► | Contain elements with chemical and physical characteristics which change progressively from metal to non-metal. | |
► | Example of elements in period 3:
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The electron arrangement of elements in the Periodic Table
■ Arrangement of elements in the Periodic Table (first 20 elements)
► | From the table, the elements in a group ○ have the same valence electrons ○ have the same chemical properties ○ exhibit physical properties which change gradually down the group |
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► | From the table, the elements in the same period have the same number of filled electron shells. |
► | By knowing the proton number of an element, we can write the electron arrangement of the element. | |
► | Thus, the Group and Period it is placed in the Periodic Table can be determined. |
✍ Worked-example 4.1(a)
An element T has a proton number of 12 and nucleon number of 24. What Group and Period does it occupy in the Periodic Table of Elements? Solution The number of electron = proton number = 12 Electron arrangement: 2.8.2 Element T has 2 valence electron. Hence element T is in Group 2 of the Periodic Table. Element T has 3 filled electron shells. Hence element T is in Period 3 of Periodic Table. |
⇲ For exercise(objective and subjective), download for free on Android OS. | ||
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