science notes class 10th ch 5
Answers
Explanation:
. The law was applicable for elements with atomic masses up to 40.
2. Properties of new elements discovered did not fit into the law of octaves.
3. In a few cases, Newlands placed two elements in the same slot to fit elements in the table.
4. He also grouped unlike elements under the same slot.
To know more about Dobereiner’s Triads and Newland’s Law of Octaves, visit here.
Mendeleev’s Periodic Table and Law
The physical and chemical properties of elements are periodic functions of their atomic weights.
Features of Mendeleev’s Periodic Table
● Twelve horizontal rows, which were condensed to 7, known as periods.
● Eight vertical columns known as groups.
● Groups I to VII subdivided into A and B subgroups.
● Group VIII doesn’t have any subgroups and contains three elements in each row.
● Elements in the same group exhibit similar properties.
Achievements of Mendeleev’s Periodic Table
1. A systematic study of elements: Elements with similar properties were grouped together, that made the study of their chemical and physical properties easier.
2. Correction of atomic masses: Placement of elements in Mendeleev’s periodic table helped in correcting the atomic masses of certain elements. For example, the atomic mass of beryllium was corrected from 13.5 to 9. Similarly, atomic masses of indium, gold, platinum etc., were also corrected.
3. Prediction of properties of yet to be discovered elements: Eka-boron, eka-aluminium and eka-silicon were the names given to yet to be discovered elements. The properties of these elements could be predicted accurately from the elements that belonged to the same group. These elements, when discovered were named scandium, gallium, and germanium, respectively.
4. Placement of noble gases: When discovered, they were placed easily in a new group called zero group of Mendeleev’s table, without disturbing the existing order.
Answer:
here is some note on Chapter 5
