(a) The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.
(b) Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
(c) State Modern periodic law.
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Answers
Answer:
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Explanation:
(a) Dobereiner Periodic Table
Advantage: To predict the atomic mass of middle element in each triad
Limitation: Dobereiner could identify only three triads
Newland Periodic table
Advantage: Every eighth element had properties similar to that of first element.
Limitation: It was only applicable up to Calcium. It included only 56 elements and no future elements were given place in the table.
Mendeleev’s Periodic Table
Advantage: Elements with similar properties could be grouped.
He also predicted the existence of new elements that had not been discovered at that time. Limitation: No fixed position was assigned to hydrogen.
Position of isotopes was not satisfactory.
Atomic masses increased in an irregular manner.
(b) Henry Moseley was the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
(c) Properties of elements are a periodic function of their atomic number
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Explanation:
Dobereiner periodic table
« Advantage: To predict the atomic mass of middle element in each triad
Limitation: Dobereiner could identify only three triads
Newland periodic table
« Advantage: Every eighth element had properties similar to that of first; co-related the properties of elements with their atomic mass.
Limitation: It was only applicable up to Calcium; only 56 elements and no future element
Mendleev's periodic table
« Advantage: Elements with similar properties could be grouped. He predicted the existence of new elements that had not been discovered at that time.
Limitation: No fixed position for hydrogen/ position of isotopes. Atomic masses do not increase in a regular manner.
Modern periodic law«
« The modern periodic law states that the physical and chemical properties of the elements are the periodic function of the atomic numbers.