Which set of quantum numbers is not allowed for an electron?
Correct answer: C. n=2, l=2, m=1, s=+1/2
- A. n=2, l=1, m=0, s=+1/2
- B. n=3, l=0, m=0, s=-1/2
- C. n=2, l=2, m=1, s=+1/2
- D. n=1, l=0, m=0, s=+1/2
Explanation
The azimuthal quantum number can only run from 0 up to n minus 1, so with n equal to 2 the value of l cannot reach 2, and the set describes a non existent 2d orbital. The other three sets satisfy every restriction, including that m lies between minus l and plus l. Checking l against n first, then m against l, resolves questions of this type quickly.
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About Quantum Numbers
Quantum numbers describe an electron's energy level, subshell, orbital orientation and spin. You examine the principal, azimuthal, magnetic and spin quantum numbers, their allowed values, orbital capacity and how they determine electronic configurations and distinguish electrons within an atom.
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