If the principal quantum number n=6, the correct sequence of filling of electrons

If the principal quantum number n=6, the correct sequence of filling of electrons will be:

  1. ns→np→(n-1)d→(n-2)f
  2. ns→(n-2)f→(n-1)d→np
  3. ns→(n-1)d→(n-2)f→np
  4. ns→(n-2)f→np→(n-1)d

Solution

According to Aufbau Principle, the electrons in an atom are filled in the increasing order of their energies. The order of orbital energies is determined by (n+l) rule. If (n+l) value is same for two orbitals, then the orbital with lower value of n is filled first.

For n = 6

6s = 6+0 = 6

6p = 6+1 = 7

5d = 5+2 = 7

4f = 4+3 = 7

So, increasing order of energy will be 6s→4f→5d→6p

The correct option is B.