This rule was first stated by Charles Janet in 1929, rediscovered by Erwin Madelung in 1936, and later given a theoretical justification by V. M. Klechkowski: Subshells are filled in the order of increasing n+l; Where two Subshells have the same value of n+l, they are filled in order of increasing n.

What is the first subshell?

For example, the 1st shell is made up of 1 subshell, s. It can therefore contain only 2 electrons. The 2nd shell is made up of 2 subshells, s and p. It can therefore contain 2+6=8 electrons.

Who discovered orbitals?

History. The term "orbital" was coined by Robert Mulliken in 1932 as an abbreviation for one-electron orbital wave function.