# Suscept. of a Diamagnet (eqn): what are these variables?

## Main Question or Discussion Point

$$\chi_m = - \frac{Z e^2 n \mu_0}{4 m} <p^2>$$

My understanding is that $$n = N/V$$, where the volume is the volume of a unit cell containing Z electrons (in this case $$n = \frac{1}{a^3}$$). The m in the denominator is related to the larmor frequency and, for a hydrogen atom, should be the mass of a proton.

$$<p^2>$$ is an expectation value of the wave function of the hydrogen atom. While this is certainly a homework question, I'm asking for general guidance about the equation. Am I correct in assuming $$m = m_p$$ is the mass of a proton? My numbers keep coming out many orders of magnitude greater so I must be missing something fundamental.