(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.
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
Mendeleev’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.
(b) Name the scientist: Henry Moseley
(c) Modern periodic law: Properties of elements are a periodic function of their atomic number.