X is an element of modern periodic table. It is surrounded by elements having atomic number 17, 34, 36 and 53.
(i) What is the atomic number of X?
(ii) Predict its position in the periodic table.
(iii) Which among these do not belong the same period?
(i) As we can see it is given that X is surrounded by all other elements given above and there are numbers given 34 and 36. So, X must have atomic number 35. And this can be verified with periodic table where atomic number 35 corresponds to Bromine.
(ii) As atomic no. 36 corresponds to Neon (Ne) having noble gas configuration: 2, 8, 18, 8 which means 18th group element so X (Br) with atomic no. 35 will lie in group just before this that is 17th group. Also, X (Br) has electronic configuration: 2, 8, 18, 7 which means it has 4 shells or n=4 and lies in 4th period. So X (Br) lies in 4th period and 17th group.
(iii) Electric configuration of elements with given atomic numbers,
Z=17: 2, 8, 7
Z=34: 2, 8, 18, 6
Z=36: 2, 8, 18, 8
Z=53: 2, 8, 18, 18, 7
It can be easily seen that elements with atomic number 34 and 36 lie in same period as have same number of shells n=4 and all other elements are from different periods.