Classification of Elements
Classification of elements: The main utility of the system is that it affords a scheme of classification of elements, which is helpful in the study of 109 elements is reduced to nine groups only. This note provides an information about elements.
Summary
Classification of elements: The main utility of the system is that it affords a scheme of classification of elements, which is helpful in the study of 109 elements is reduced to nine groups only. This note provides an information about elements.
Things to Remember
- Classification of elements: The main utility of the system is that it affords a scheme of classification of elements, which is helpful in the study of 109 elements is reduced to nine groups only.
- Mandeleev's periodic table was based on atomic mass. In 1913, Mosley from his studies on x- rays found that the atomic number is the more fundamental property of an element than its atomic mass. Thus, atomic number was adopted as the basis of modern periodic table.
- Modern periodic law: The properties of elements are a periodic function of their atomic numbers.
MCQs
No MCQs found.
Subjective Questions
Q1:
Calculate the range and the coefficient of range from the data:
5, 10, 15, 20, 25, 30, 35, 40, 45
Type: Short Difficulty: Easy
<p>Here,<br />largest item (L) = 45 <br />Smallest item (S) = 5 <br />∴ Range = L - S = 45 - 5 = 40<br />Coefficient of range = \(\frac{L - S}{L + S}\)<br />= \(\frac{45 - 5}{45 + 5}\) <br />= \(\frac{40}{45}\)<br />= 0.8</p>
Q2:
Calculate the range and the coefficient of range from the following data:
| Income in Rs | 100 | 200 | 300 | 400 | 500 | 600 |
| No. of persons | 20 | 25 | 30 | 35 | 40 | 45 |
Type: Long Difficulty: Easy
<p>Here, <br />Largest item (L) = 600<br />Smallest item (S) = 100<br />∴ Range = L - S <br />or, 600 - 100<br />or, 500<br />Coefficient of Range = \(\frac{L - S}{L + S}\)<br />= \(\frac{600 - 100}{600 + 100}\)<br />= \(\frac{500}{700}\)<br />= 0.714</p>
Q3:
Calculate the range and the coefficient of range from the following:
| Age (in year) | 10 - 20 | 20 - 30 | 30- - 40 | 40 - 50 | 50 - 60 | 60 - 70 |
| No. of person | 12 | 17 | 29 | 22 | 27 | 13 |
Type: Short Difficulty: Easy
<p>Here, <br />Upper limit of the highest class (L) = 70<br />Lower limit of the smallest class (S) = 10 <br />∴ Range = L - S <br />= 70 - 10 <br />= 60 years<br />Coeffient of range = \(\frac{L - S}{L + S}\)<br />= \(\frac{70 - 10}{70 + 10}\) <br />= \(\frac{60}{80}\)<br />= 0.75</p>
Q4:
Calculate the range and the coefficient of range from the following data:
| Age (in years) | 16 - 20 | 21 - 25 | 26 - 30 | 31 - 35 |
| No. of persons | 12 | 17 | 29 | 22 |
Type: Long Difficulty: Easy
<p>Since age is a continuous variable, we should first change in classes into exclusive classes.</p>
<table style="height: 51px;" width="468">
<tbody>
<tr>
<td>Age (in years)</td>
<td>15.5 - 20.5</td>
<td>20.5 - 25.5</td>
<td>25.5 - 30.5</td>
<td>30.5 - 35.5</td>
</tr>
<tr>
<td>No. of persons</td>
<td>10 </td>
<td>15</td>
<td>17 </td>
<td>8</td>
</tr>
</tbody>
</table>
<p>Here,<br /> upper limit of the highest class (L) = 35.5<br />lower limit of the smallest class (S) = 15.5<br />∴ Range = L - S<br />= 35.5 - 15.5<br />= 20 years<br />Coefficient of Range = \(\frac{L - S}{L + S}\)<br />= \(\frac{35.5 - 15.5}{35.5 + 15.5}\)<br />= \(\frac{20}{51}\) <br />= 0.39<br /><br /></p>
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Classification of Elements
Applications of Periodic table
- Classification of elements: The main utility of the system is that it affords a scheme of classification of elements, which is helpful in the study of 109 elements is reduced to nine groups only.
- Prediction of new elements: Mendeleev left many gaps in his original table and their atomic mass, physical and chemical properties of the elements to be discovered: Later on these new elements to be discovered.
- Correction of doubtful atomic masses: Many doubtful atomic masses were corrected with the help of this classification.
Mendeleev's periodic table
Mendeleev's periodic table was based on atomic mass. In 1913, Mosley from his studies on x- rays found that the atomic number is the more fundamental property of an element than its atomic mass. Thus, atomic number was adopted as the basis of the modern periodic table.
Modern periodic table
The properties of elements are a periodic function of their atomic numbers. This means that if the elements are arranged in order of their atomic number, then elements with similar properties are repeated after a regular interval.
Modern periodic law:
The properties of elements are a periodic function of their atomic numbers. This means that if the elements are arranged in order of their increasing atomic number, then elements with similar properties are repeated after a regular interval. The periodic table based on this law is known as the modern periodic table.
Description of the long form of periodic table:
- In this periodic table, the elements are arranged in order of their increasing atomic number.
- There are seven periods. The first period contains two elements and is the shortest period. The second and the third periods containing 8 elements each are called short periods. The fourth and the succeeding periods are the long periods.
- The table has 18 vertical columns, but the number of the group is 16 only. This is because group VIII has three vertical columns.
Advantages of modern periodic table:
- The modern periodic table is based on the most fundamental property, the atomic number of elements, while Mendeleev's periodic table is based on the atomic masses of elements.
- In Mendeleev's periodic table, there are several anomalies, e.g. the position isotopes, wrong order of atomic masses of atomic masses of some elements, etc. In this long form of the periodic table, these anomalies have been removed.
- In this modern periodic table, the sub-groups A and B are clearly separate because the elements belonging to subgroup B have slightly different properties. In Mendeleev's periodic table, the sub-groups are kept together.
Lesson
Matter
Subject
Science
Grade
Grade 8
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