The distribution of electrons into different orbits of an atom, as suggested by Bohr; is

According to the Bohr-Bury scheme, the distribution of electrons in different orbits or shells of an atom is governed by the formula 2n², where 'n' represents the orbit number or energy level. For the first shell (K-orbit, n=1), the maximum capacity is 2(1)² = 2 electrons. For the second shell (L-orbit, n=2), the capacity is 2(2)² = 8 electrons. For the third shell (M-orbit, n=3), the capacity is 2(3)² = 18 electrons. While the outermost shell of an atom cannot accommodate more than 8 electrons regardless of its theoretical capacity, the total capacity of the M-shell as defined by Bohr's model is 18. This systematic arrangement explains the electronic configurations of elements like Argon (2, 8, 8) and the theoretical limits of the K, L, and M shells.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.3 HOW DO METALS AND NON-METALS REA ALS REACT? > p. 47