Explain quantitatively the order of magnitude difference between the diamagnetic susceptibility of `N_2(-5xx10^-9)` (at STP) and `Cu(-10^-5)`.

Explanation

Density of nitrogen, `rho_(N_2)=(28g)/(22.4litre)=(28g)/(22400c c)`
We know, density of copper, `rho_(cu)=8g//c c`
`:. (rho_(N_2))/(rho_(Cu))=(28)/(22400)xx1/8=1*6xx10^-4`.
Given, `(chi_(N_2))/(chi_(cu))=(5xx10^-9)/(10^-5)=5xx10^-4` …(i)
We know that `chi= ("intensity of magnetisation"(I))/("magnetising force" (H))=I/H=("magnetic moment"(M)//volume(V))/(H)`
`=(M)/(HV)=(M)/(H["mass"(m)//"density"(rho)])=(Mrho)/(Hm)`
`:. chiproprho` for the given value of `M//Hm`.
Hence, `(chi_(N_2))/(chi_(Cu))=(rho_(N_2))/(rho_(Cu))=1*6xx10^-4` ...(ii)
From (i) and (ii), we note that the major difference in susceptibility of `N_2` and `Cu` is due to their density.