Question

What is (n+1) rule? Why is 4s orbital filled before 3d orbital's?

Answer 1

Answer:

Due to low energy of 3D orbital

Explanation:

Answer 2

Explanation:

With the help of n+l rule we can arrange orbitals belonging to different shells on the basis of their energy as-

First find the value on n+l, here n=principal quantum no. and l=azimuthal quantum no. of the required orbitals .Then lower the value of n+l lower will be the respective orbital's energy.In case if n+l is equal for certain orbitals then lower the value 'n' lower is the energy.Now understand this with these examples-

n+l rule for

1s=1+0=1(here,n=1 and l=0)

2s=2+0=2(here, n=2 and l=0)

hence,energy of 1s is lower than 2s

now,

3d=3+2=5(here,n=3 and l=2)

4s=4+0=4(here,n=4 and l=0)

hence, 4s orbital is filled before 3d orbital.

Hope it helps!