Why `3d` sub-shell has higher energy than `4s` sub-shell in a muti-electron atom?

Why can 2p sub-shell accommodate more electrons than 2s sub-shell ?

M-shell contains sub shell

The number of orbitals in d sub-shell is

What is the relation between sub-shells and no. of electrons in it ?

Which sub-shell has maximum energy (poly-elecronic system ) :

The seqence of filling electgron in sub-shells of element with few exception in d-block and f-block element is govened by.Aufbau principle followed by Hund's rule and pauli's ecxclusion principal a. The electron prefers to enter into sub-shell with lower (n +l) values The energy for any sub-shell of an element other than hydrogen is praportioanal to the sum of principal quantum number (n) and angular momentum quantum number b. If (n + l) value is same for many sub-shell with lowest n value c. i. Fulfiling sub-shell is more stable ii. Half filled sub-shell is more stable less than half filed Which pair of sub-shell has same energy for above described excriptional element under rule (a) ?

Which of the following has non-spherical sub-shell of electron ?

Which of the following has non-spherical sub-shell of electron ?

The two electrons in K sub-shell will differ in