Question

an element "X" has mass number 35 and the number of neutrons is 18. Identify the group number and period of "x".

Answer 1

it is chlorine
it will lie in 17 period
it will lie in 3rd period

Answer 2

atomic no. of X = Mass no. of X - no. of neutrons
= 35 - 18 = 17
Electronic configuration will be 2,8,7

Therefore group is 17 and period is 3.
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