## Chemistry: The Central Science (13th Edition)

in a many-electron atom, the energy of an orbital increases with increasing value of $l$: $$ns\lt np\lt nd \lt nf$$
In a many-electron atom, due to the electron-electron repulsions, the energies of different subshells in a given shell are different according to the following rule: "In a many-electron atom, for a given value of $n$, the energy of an orbital increases with increasing value of $l$" In other words, in a many-electron atom, for a given value of $n$, we have the following orbitals in order of increasing energy $$ns\lt np\lt nd \lt nf$$