Question

Which of the following quantum number combinations is not allowed in a ground-state atom?

(2, 1, 1, -½)
(8, 7, -7, +½)
(5, 5, -5, +½)
(1, 0, 0, +½)

Answer 1

The third option. The angular quantum number ($l$) can be any integer between 0 and $n-1$. Therefore, for the third option, $l$ can be 0, 1, 2, 3, or 4—but not 5.