Which set of quantum numbers is not allowed for an electron?

  • 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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