An element 'X' has mass number 35 and the number of neutrons, is 18

CBSE Class 10 CBSE Class 10 Science
1

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

2

Atomic no. of X = Mass No. of X - No. of protons
As,
No. of protons = No. of neutrons
∴ No. of Protons = 18
Mass no. of X = 35
So,
Atomic no. of X = 35-18 = 17
Electronic configuration = 2, 8, 7.

  1. 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)
  2. Period No. = 3