Principal Quantum Numbers Please help

[antgoblue]

What is the principal quantum number of the s and p valence electrons in the following chemical elements?  A) silicon B) aluminum C) boron D) nitrogen E) calcium F) krypton. Thank You

[spock]

The principal quantum number indicates the energy level that an electron is located in.  I assume that you want the principal quantum number for an electron in the valence shell of the atoms listed.  It doesn't matter what sub-shell the electron is in (that's what the 2nd quantum number tells you!).  So,
for Si with valence electrons in the 3rd energy level, the principal quantum # would be 3.

[Chemistry_Guru]

Just remember that Principle quantum number is the most important quantum number. As it determines to a large extent the energy of an electron. It also determines the average distance of an electron from the nucleous.
if we speak of Al , B , N, Ca, Kr....
Element                      Principle quantum number
  Al                                    # 3.
  B                                     # 2.
  N                                     # 2.
  Ca                                   # 4.
  Kr.                                   # 4.

I hope that should help.