(a) The modernperiodictablehas beenevolvedthrough the early attempts of Dobereiner, Newlandand Mendeleev. List one advantageand one limitation ofall the threeattempts. (b) Namethe scientist who firstof allshowedthat atomicnumber of an element is a more fundamentalpropertythan its atomic mass. StateModernperiodiclaw.

(a) The modernperiodictablehas beenevolvedthrough the early attempts o

1.	(a) The modernperiodictablehas beenevolvedthrough the early attempts of Dobereiner, Newlandand Mendeleev. List one advantageand one limitation ofall the threeattempts. (b) Namethe scientist who firstof allshowedthat atomicnumber of an element is a more fundamentalpropertythan its atomic mass. StateModernperiodiclaw.
Answer» Solution :(a) Dobereiner's Triads Advantage : It was the first genuine scientific attempt to group elements with similar characteristics in traids. Limitation : The number of triads was limited to a few elements only. Therefore, this attempt could not gam IMPORTANCE. Newland's Law of Octaves Advantage : This law for the first time gave the idea of groups. Moreover, the elements were arranged in increasing order of ATOMIC MASSES. Limitation : This classification was successful only upto calcium. Mendeleev's Classification Advantage : Mendeleev's classification laid che foundation of the Modern Periodic Table. He was successful. in arranging large number of known elements into groups and periods Limitation : The basis of classification as given by Mendeleev's periodic law was not correct. This led to MANY LIMITATIONS e.g. position of hydrogen, position of isotopes etc. (a) It was given by Moseley in the form of Modern Periodic Law. (c) According to Modern Periodic Law 'physical and chemical properties of elements are the periodic function of their atomic numbers.