What is the maximum number of electrons that can occupy the first shell of an atom ?

The distribution of electrons in different orbits or shells of an atom is governed by the Bohr-Bury scheme. According to this rule, the maximum number of electrons that can be accommodated in a shell is given by the formula 2n2, where 'n' is the orbit number or energy level index.

• For the first shell (K shell), n = 1.
• Applying the formula: 2 × (1)2 = 2 × 1 = 2.

Therefore, the maximum number of electrons that can occupy the first shell is 2. For comparison, the second shell (L shell, n=2) can hold a maximum of 8 electrons (2 × 22), and the third shell (M shell, n=3) can hold up to 18 electrons (2 × 32).