the spectroscopic notation (also called spdf notation) electron configuration of Ni?

Ni is number ##28## on (Atomic number is ## 28##)

spdf ##Ni : ## ##1s^2## ##2s^2## ##2p^6## ##3s^2## ##3p^6## ##3d^8## ##4s^2##

To check the total of all powers: ##2+2+6+2+6+8+2 = 28##

The power of the subshell(s, p, d, f) gives the number of electrons on each subshell.

maximum values for subshells: s ##=2## p ##=6## d ##= 10## f ##=14##

Note : The reason why i didn't fill the ##3d## with ##10##, but rather put ##2## in ##4s## and 8 in the ##3d## is that,

##4s ## subshell is lower than the ##3d## subshell and so it must be filled first.

So you fill it with ##2## (maximum for an ##s## subshell) before putting the rest in ##3d##

Important fact :

The ##4s## subshell is always filled before the the ##3d## .