Quantum Numbers
Which set of quantum numbers is NOT possible for an electron in an atom according to the rules governing quantum mechanical description of electrons?
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About This Question
- Subject
- chemistry
- Chapter
- atomic structure
- Topic
- quantum numbers
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
n=4,l=3,ml=+4,ms=+1/2
The rules governing quantum numbers are: n must be a positive integer; l ranges from 0 to n-1; m_l ranges from -l to +l; m_s is either +1/2 or -1/2. Examining each option: n=3, l=2 is valid because l ≤ n-1=2; m_l=-2 is valid since |m_l| ≤ l=2; m_s=+1/2 is valid. n=2, l=1 is valid; m_l=0 is within range; m_s=-1/2 is valid. For n=4, l=3: l=3 ≤ n-1=3 is valid, but m_l=+4 is NOT valid because m_l can only range from -3 to +3, so +4 exceeds the limit. Hence this set is impossible. n=1, l=0, m_l=0, m_s=-1/2 perfectly satisfies all rules for a 1s electron. The invalid option n=4, l=3, m_l=+4 violates the rule that m_l cannot exceed l in magnitude. This is a standard NCERT/JEE concept on quantum number restrictions. Plausibility check: m_l=+4 with l=3 clearly breaks the boundary condition, confirming it as the impossible set.
This easy difficulty chemistry question is from the chapter atomic structure, covering the topic of quantum numbers. It appeared in the 2025 exam.
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