Q. An element with atomic number 20 will be placed in which period of the Periodic Table?
A) 1
B) 2
C) 3
D) 4
Explanation
(d)
$1s^{2},\ 2s^{2}2p^{6},\ 3s^{2}3p^{6},\ 4s^{2}.$ Principal quantum number is 4, so it belongs to 4th period
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.