OAVS Class 10 Science: Chapter 5; periodic classification of elements
Today in this article we are providing students the study material of NCERT/OAVS Class 10 Science Chapter 5: Periodic Classification of Elements. Now ncert books have been made mandatory for the students of OAVS & EMRS in Odisha and this step taken by the Govt of odisha is likely to be very beneficial in the interest of the students from the new session. All that is needed is that the students should prepare their study strategy according to the changed syllabus and preparing themselves.
Also, after the changes in the Odisha Board, it has become easier for the students to appear in other types of competitive examinations along with the examination as compared to earlier. In this context, it is expected that now the students of Odisha Board will get a better chance to move forward than before.
Here we are listing down some important topics of this chapter for the students so that the students cover all the topics thoroughly while studying and to get the complete chapter, the link is given below the topics, on clicking which the students can read the whole chapter. You can get PDF.
What is Periodic Table ?
•》The periodic table is a classification of elements in terms of their atomic number, electron configuration, and recurring chemical properties. It is a useful tool for organizing data about the chemical elements and understanding the relationships between them.
1. Dobereiner's Triad :
•》According to the German chemist Johann Wolfgang Döbereiner the atomic mass of the middle element was approximately the average of the atomic masses of the other two elements in the triad. In the year 1817, He tried to arrange the elements in a sequence with similar properties in the groups. He arranged 3 elements in a group having similar properties. So he called these groups 'triads'. Döbereiner placed the elements in the order of increasing atomic mass in the group. Döbereiner was just able to identify 3 triads from the elements known in 1817.
Döbereiner's triads :
1st Element Li Ca Cl
2nd Element Na Sr Br
3rd Element K Ba I
2. Newlands' Octave Theory :
•》John Newlands an English Chemist, tried to arrange the known elements in the order of increasing atomic masses in 1866, by inspiring from Döbereiner's triads. After Döbereiner's triads the other chemist also imspired to find relationship between the atomic mass and properties of the elements. According to him the properties of every eighth element had similar properties to that of the first. He just compared this method to the octave notes (sa, re, ga, ma, pa, da, ni) found in music. Therefore, he named it the 'Law of Octaves'. Later it is known as 'Newlands' Law of Octaves'. According to the Newlands' law of Octaves, the properties of lithium and sodium were found same. Sodium is the 8th element after lithium. Similarly, beryllium and magnesium resemble each other and vice versa.
3. Mendeleev's Periodic Table :
•》After the rejection of Döbereiner's triad & Newland's law of octaves many chemist triad to find out relation between properties of elements and the atomic mass of that element. But the main credit goes to a russian scientist, DI Mendelèev who was the important contributor of development of periodic table.
At the time of his work just 63 elements were known. He examined the relationship between atomic mass and the properties of that element. For chemical properties he considered two element (i) Oxygen (ii) Hydrogen as are most reactive elements and formed compound with most elements. He considered the formation of hydride and oxides as basic properties of one elements. According to him 'the properties of elements are the periodic function of their atomic masses'.
4. Achievements of Mendeleev's Periodic Table:
While developing the periodic table Mandeleev just left some places among the elements and he predicted that new elements will take place in the gap. So he just named that elements by prefixing a sanskrit word - Eka' (one) e.g Eka-boron, Eka-aluminium, Eka-silicon.
Later Eka-boron , Eka-aluminium and Eka-silicon were replaced by Scandium, Gallium and Germanium respectively as they had the similar physical and chemical properties.
5. Arranging by Arrangement - Modern Periodic Table
6. Position of Elements in the Modern Periodic Table
7. Atomic Size
8. Metallic and Non-metallic Properties
Some Key Points of the topic :
•》On the basis of similarities in their properties elements are classified.
•》Döbereiner grouped the elements into triads and Newlands gave the Law of Octaves.
•》According to the chemical properties and increasing order of their atomic masses, Mendeleev arranged the elements.
•》Elements in the Modern Periodic Table are arranged in 18 vertical columns called groups and 7 horizontal rows called periods.
•》Elements arranged in the table shows the periodicity of properties including atomic size, valency or combining capacity and metallic and non-metallic character.
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