The Question is from neet-chemistry , and it was created by the author Mr. S M HUSSAIN

Question

An element has the electronic configuration $1s^22s^22p^63s^23p^5$.  In which period and group is this element located?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Electronic configuration and its relation to periodic table position.
 **Related Topics**: Periods, groups, valence electrons, atomic number.
 **Prerequisites**: Understanding of electron shells, subshells, and the filling of orbitals according to Aufbau principle.
## SOLUTION PATHWAY
**Given Information**:
  Electronic configuration: $1s^22s^22p^63s^23p^5$
**Method & Steps**:
 1. Determine the period:
  Reasoning: The period number corresponds to the highest principal quantum number (n) occupied by an electron. In this configuration, the highest occupied energy level is n=3.
  Formula/Rule: None
 2. Determine the group:
  Reasoning: The group number is determined by the number of valence electrons (electrons in the outermost shell).  The outermost shell is n=3, and it contains $3s^23p^5$ electrons, giving a total of 7 valence electrons (2 + 5 = 7).
  Working: Group number = Number of valence electrons. Group number = 7.
  Key Point: Group 17 (also known as Group VIIA or halogens) elements have 7 valence electrons.
 3. Final step:
  Result: Period 3, Group 17
  Verification: The configuration indicates 3 shells (n=1,2,3) and 7 valence electrons, consistent with Period 3, Group 17.
 ## OPTION ANALYSIS
A :x: Incorrect period. The highest principal quantum number is 3, indicating Period 3, not Period 2.
B :x: Incorrect group. The element has 7 valence electrons, placing it in Group 17 (halogens), not Group 15 (pnictogens).
C ✓: Correct period and group. The electronic configuration corresponds to Period 3 and Group 17.
D :x: Incorrect period. The highest principal quantum number is 3, indicating Period 3, not Period 4.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing period and group numbers: Remember that the period number is the highest energy level, while the group number is related to valence electrons.
  2.Miscounting valence electrons: Carefully add electrons in the outermost shell to determine the group number.
 **Quick Tips**:
  1.Identify the highest 'n' value for the period and the number of electrons in the outermost shell for the group.
  2.Remember the group numbers correspond to the number of valence electrons.

Mr. S M HUSSAIN · Answer

Period 2, Group 17

Mr. S M HUSSAIN · Answer

Period 3, Group 15

Mr. S M HUSSAIN · Answer

The correct Option is "Period 3, Group 17"

Mr. S M HUSSAIN · Answer

Period 4, Group 17

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