A – 2, 2
B – 2, 8, 5
C – 2, 7
D – 2, 8, 2
a) Find the elements belonging to the same period?
b) Find the elements belonging to the same group.
c) ‘C’ belongs to which period and group?
a) B, D and A, C belong to the same period because the number of shells are same.
b) A and D belong to the same group because the number of electrons in the outermost shell is the same.
c) ‘C’ belongs to the second period and 17th group.