If hydrogen atoms (in the ground state) are passed through an homogeneous magnetic field, the beam is split into two parts.This interaction with the magnetic field shows that the atoms must have magnetic moment.However, the moment cannot be due to the orbital angular momentum since l=0. Hence one must assume existance of intrinsic angular momentum, which as the experiment shows, has only two permitted orientations. Spin of the electron produces angular momentum equal to `s=sqrt(s(s+1))h/(2pi)` where s=+`1/2`. Total spin of an atom =+`n/2 or n/2` where n is the number of unpaired electron. The substance which contains species with unpaired electrons in their orbitals behave as paramagnetic substances.The paramagnetism is expected in terms of magnetic moment. The magnetic moment of an atom `mu=sqrt(s(s+1))(eh)/(2pimc)=sqrt(n/2(n/2+1))(eh)/(2pimc)s=n/2` `rArrmu_s=sqrt(n(n+2))B.M.` n=number of unpaired electrons 1. B.M.(Bohr magneton)`=(eh)/(2pimc)` If magnetic moment is zero the substance is diamagnetic. Which of the following is a paramagnetic substanceA. `Mg^(2+)`B. `Cu^(+)`C. `Mn^(+7)`D. `Ti^(+2)`