Answer:-
[Kr] 5s1
Explanation:-
Atomic number of rubidium = 37
Atomic number of Kr = 36
So only 1 electron needs to be assigned an orbital.
Kr is also the last element of the fourth period
So the shell number for the 1 electron will be 5 since it is after Kr
Since s subshell is filled first the electron will go into 5s.
Hence the electron configuration for rubidium (Rb) in noble-gas notation is
[Kr] 5s1
