The maximum number of electrons that can be accommodated in each shell depends on the formula 2n2 , where n is the number of the given shell from the nucleus. K is the first shell.
K shell have only one subshell. All other shells have more than one subshell named as s,p,d,f. each of the main energy level contains the same number of subshells as its serial number. Thus the K shell, which is the first has 1 subshell. L shell has 2 subshells, M shell has 3 subshells and n shell has 4 subshells as given below: