Question

4s-orbital has less energy than 3d-orbitals.

Answer 1

i thik 3d filled firstly than 4s orbital.

Answer 2

according to (n+l) rule both having same energy ,but n value is different 3d has 3 and 4s has 4 .which value is lesser it has maximum energy so 4 is bigger hence 4s orbital has lesser energy than 3d