Question

how to calculate period and group of elements if atomic number is given

Answer 1

elements are placed in the periodic table according to their atomic number and atomic mass number periodic table s p d and f block elements are there according to the valency of the element loses electrons are placed in S block elements accept electrons there please place in P block Hina transition elements are placed below the periodic table stable elements are placed in 18th group

Answer 2

 Let we are Given Atomic No. = 17

So, Electronic Configuration = 2,8,7
           No of Shells = Period No. = 3   
   and, 10+ No of Valence electrons = Group. No. = 10+7 = 17 (only for                                          elements which have valence electrons 3 or 3+)