Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30 respectively belong to the same period?
  1. A, B, C
  2. B, C, D
  3. A, D, E
  4. B, D, E

AcademicChemistryNCERTClass 10

Correct answer: (b) B, C, D

Explanation: The 2nd period contains elements with atomic numbers 3(Li), 7(N), 10(Ne). Since the second period has elements having atomic numbers 3 to 10.

Updated on 10-Oct-2022 13:19:20