Consider the hypothetical situation where the azimuthal quantum number,$l$,takes values $0, 1, 2, \ldots, n+1$,where $n$ is the principal quantum number. Then,the element with atomic number

• A
  $13$ has a half-filled valence subshell
• B
  $9$ is the first alkali metal
• C
  $8$ is the first noble gas
• D
  $6$ has a $2p$ valence subshell