Electron Shells

The protons are in the nucleus of the atom, electrons are located in shells, in order of increasing energy level.

The shells of atoms are in the following order of increasing energy level:

K (1st shell and lowest in energy level)

L (2nd shell)

M (3rd shell)

N (4th shell and highest in energy level)

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The maximum number of electrons a shell can contain is given by 2(n2) where n is shell number or principal quantum number.

K shell, n = 1

L shell, n = 2

M shell, n = 3

N shell, n = 4