An element ‘X’ has mass number 35 and the number of neutrons, is 18. Identify the group number and period of “X”.
Atomic no. of X = Mass No. of X - No. of protons
No. of protons = No. of neutrons
∴ No. of Protons = 18
Mass no. of X = 35
Atomic no. of X = 35-18 = 17
Electronic configuration = 2, 8, 7.
- As the no. of valence electrons is more than two, then group no. is equal to the sum
of valence electrons and ten.
Therefore, Group no. = 17 (10 + 7)
- Period No. = 3