Question

Which of the given elements A , B , C , D , E with atomic number 2 , 4 , 7 , 10 , 20 respectively belong to the same period ?

Answer 1

Answer:

A = 2 = helium

B = 4 = beryllium

C = 7 = nitrogen

D = 10 = Neon

E = 20 = calcium

among these, elements B,C,D i.e beryllium, nitrogen, Neon belongs to the same period (period 2)

and the others,

A= helium(period 1) & E = calcium(period4)

hope this helps :)