Explain the energy order of orbitals in multielectron atoms.

(N/A) In multielectron atoms,the energy of an orbital depends on both the principal quantum number $(n)$ and the azimuthal quantum number $(l)$.
$1$. In a multielectron atom,the electron experiences attraction from the nucleus and repulsion from other electrons.
$2$. The inner electrons shield the outer electrons from the full nuclear charge,a phenomenon known as the shielding effect. The effectiveness of this shielding depends on the shape of the orbital $(s > p > d > f)$.
$3$. Due to different shielding effects,orbitals within the same principal shell $(n)$ have different energies. For example,in the $n=3$ shell,the energy order is $3s < 3p < 3d$.
$4$. The energy of orbitals is generally determined by the $(n+l)$ rule. Orbitals with a lower $(n+l)$ value have lower energy. If two orbitals have the same $(n+l)$ value,the one with the lower $n$ value has lower energy.