State Hund's rule and its importance in filling the orbitals in various energy levels, take atomic number 17 as an example.

The total number of atomic orbitals in fourth energy level of an atom is.

What is the maximum number of orbitals in any energy level ?

An atom has x energy level , then total number of lines in its spectrum are :

The total number of subshells in fouth energy level of an atom is

The electron are distributed around the nucleus in various energy levels shells, subshells and orbitals. A set of quantum numbers completely describe the position and total energy of electron in an atom. The various permitted values of quantum numbers are : principal, n = 1,2,3,4...... azimuthal , l = 0,1,2,....(n -1) magnetic, m_l = -l .....0 .....+ l spin, m_s = +1//2 and -1//2 . How many orbital (of all kind) are possible for n = 3 energy level?

If Hund's rule is not followed and energy of orbitals is governed by"n" only and no (n+1) rule then