Question

which of the following is not permitted as a plausible orbital designation according to quantum theory.

Explanation:

In quantum theory, the principal quantum number \(n\) and the angular - momentum quantum number \(l\) have the relationship \(l = 0,1,\cdots,n - 1\). For a \(d\) - orbital, \(l=2\). If \(n = 2\), then \(l\) can only be \(0\) (s - orbital) or \(1\) (p - orbital). So, the \(2d\) orbital is not permitted.

Answer:

C. \(2d\)