Chemistry S & P Block Elements ETEA 2019
PMDC Verified Question 75 of 104
How many elements are there in the 3 period of periodic table?
A
18
B
8
C
32
D
10
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 8
Concept:

The number of elements in a given period corresponds to the number of electrons required to fill the sublevels associated with that principal quantum number.

Solution:

  • The 3rd period of the periodic table involves the filling of the 3s and 3p subshells.
  • The 3s subshell can hold a maximum of 2 electrons.
  • The 3p subshell can hold a maximum of 6 electrons.
  • Total electrons = 2 + 6 = 8.
  • Therefore, the 3rd period contains exactly 8 elements (Sodium to Argon) and is classified as a "short period".


Why other options are incorrect:

  • 18: Corresponds to periods 4 and 5 (which include the d-block).
  • 32: Corresponds to period 6 (which includes both d-block and f-block).
  • 10: Is the capacity of the d-subshell alone, not a full period.

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