Question

If n = 6, the correct sequence for filling of electrons will be,
a) ns → (n – 2) f → (n – 1)d → np
b) ns → (n – 1) d → (n – 2) f → np
c) ns → (n – 2) f → np → (n – 1) d
d) none of these are correct

Answer 1

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 A.

Answer 2

Answer:

The order of orbital energies is determined by (n+l) rule.

For n = 6

6s = 6+0 = 6

6p = 6+1 = 7

5d = 5+2 = 7

4f = 4+3 = 7

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