o Sub-shells are actually sub-levels (energy levels) for an atom. The number of sub-shells is equal to the number of the principal shell i.e. the number of principal quantum number n. Also, the azimuthal quantum number l decides the orbital angular momentum ( presence of orbitals) and for a certain n, the values of l (subshells) would be 0 to (n-1)

o Hence e for 3^rd shell or orbit, there are 3 sub-shells (0,1,2) that is, 3s, 3p and 3d.

• The 3s –subshell has only one orbital.

• The 3p-subshell has 3 orbitals.(p_x ,p_y , p_z)

• The 3d-subshell has 5 orbitals(d_xy,d_yz,dxz,d_z²,d_x²_-y² )

Hence total orbitals are = 1 +3+5 = 9.