Question

the salient features of the modern periodic table

Answer 1

 1. it has 18 groups of elements and 7 periods of elements.



2. there is a periodicity in the electronic configuration of elements. by separation of elements in the mendeleeffs classification of elements, the position of isotopes could not be explained.wrong order of atomic masses.



3.so it leads to classifying modern periodic table. mostly worked on x-ray spectra of elements and established that the atomic number is equal to the total nuclear charge and it is more fundamental characteristic of an element than atomic weight...







------------------  in this way modern periodic table classified. ------------------

Answer 2

1.modern periodic table have 18 vertical columns called groups and 7 horizontal rows are called periods.
2.the basis of classification of element is atomic numbers
3.hydrogen have acquired a unique position
4.no.of periods determine the no.of shells present in an element..where as no..of groups determine the no.of valence electrons. .....
5.it have s block.....p block....d block.....and....f block....