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QUESTION
Q10) The electronic configuration of an element is 1s2 2s2 2p6 3s2 3p3. What is the atomic number of the element which is just-below the above element in the periodic table? [ CBSE PMT 1995]




SOLUTION

Given configuration atomic number is 15 which is in third period
Thus required element is in fourth period=15 + 18=33
Answer: (a)