In an atom, electrons are arranged in energy levels or shells, which are regions around the nucleus where electrons are likely to be found. The shells are labeled using the letters K, L, M, N, and so on, starting from the innermost shell closest to the nucleus.
Each shell has a maximum capacity of electrons it can hold, and the capacity is given by the formula 2n^2, where n represents the shell number. For example, the first shell (K shell) can hold a maximum of 2 electrons (2 * 1^2 = 2), the second shell (L shell) can hold a maximum of 8 electrons (2 * 2^2 = 8), and so on.
The distribution of electrons in the shells follows the "aufbau principle" and the "Pauli exclusion principle." According to the aufbau principle, electrons occupy the lowest available energy level first before moving to higher levels. The Pauli exclusion principle states that each orbital within a shell can hold a maximum of two electrons, with opposite spins.
Here is a summary of the number of electrons each shell can contain:
- K Shell (first shell): Maximum of 2 electrons
- L Shell (second shell): Maximum of 8 electrons
- M Shell (third shell): Maximum of 18 electrons
- N Shell (fourth shell): Maximum of 32 electrons
- O Shell (fifth shell): Maximum of 50 electrons
- And so on...
It's important to note that not all atoms have electrons occupying all available shells. The number of electrons in an atom depends on the atomic number of the element and its electron configuration.