Atomic number of Calcium Ca is 20.
We know that there are four quantum numbers which can be assigned to "describe" any electron in an atom. Each electron has a unique set of these four quantum numbers.
n= principal quantum number, which defines the energy level of the electron.
l= azimuthal (angular) quantum number defining the energy sub-level. Its values range from 0 to (n−1); 0=s,1=p,2=d,3=f
m(l)= magnetic quantum number indicating orbital within a sublevel. Range from −l through 0 to +l
m(s)= spin quantum number. It identifies an electron within an orbital and can have either of the two values +12and−12
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The electronic configuration of calcium is:
1s2;2s2,2p6;3s2,3p6;4s2 or [Ar]4s2
it is evident that the 19th electron goes to 4s energy level.
As such for it n=4,l=0
We know that for l=0,m(l)=0 only.
Hence magnetic quantum number m(l) of 19th electron of calcium is =0
