$$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^1 5d^1$$
Here, the notation "1s^2" indicates that the first electron shell (n = 1) has two electrons and "2s^2" indicates that the second electron shell (n = 2) has two electrons, and so on.
To summarize, the ground state electron configuration of Lanthanum can be simplified as [Xe] 5d^1 6s^2 where [Xe] represents the electron configuration of Xenon (Xe), which is the noble gas that precedes Lanthanum in the periodic table.
