The Only Valid Electron State and Shell Designation Among the Following

Multiple Choice

The only valid electron state and shell designation among the following is

A) $2 s , \mathrm {~K} ( n = 1 )$ shell.
B) $1 p , \mathrm {~K} ( n = 1 )$ shell.
C) $2 p , \mathrm {~L} ( n = 2 )$ shell.
D) $1 s , L ( n = 2 )$ shell.
E) $3 f , \mathrm { M } ( n = 3 )$ shell.