Q3 of 33 Page 1

An element “X” has mass number 35 and the number of neutrons is 18. Identify the group number and period of “X”.

Mass number = 35; number of neutrons = 18

So atomic number = Mass number – number of neutrons


Atomic number = 35 – 18


= 17


Group number = 17


Electronic configuration = 2, 8, 7


So period number = 3


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