Question

In a hydrogen atom the 2 s and 2 p orbitals have the same energy. However, in a boron atom, the 2s electrons have a lower energy than the 2 p . Explain this in terms of the shape of the orbitals.

Answer 1

in hydrogen atom there is only one electron. it is present in first orbit 1s . it is lower energy orbital in hydrogen.

so remaining orbitals are empty. so they should have same energy . because no electrons are present in these orbitals

in case of boron configuration -1s² 2s² 2p¹

here n + l value for 2s orbital = 2+0 = 2

n+ l value for 2p orbital   = 2 +1 = 3

n+ l value lowest orbital is lowest energy orbital .

and also spherical shape orbital very close to nucleous than dumbel shape orbital it is due to pentration power is more for s -orbital.