1. Mass of cube = volume × density = a3ρ ……………. (1)
Mass of N particles = N × Mass of one particle
= N × \(\frac{M}{N_A}\) (M = Gram Atomic Mass) …………. (2)
2. The equations (1) & (2) represent the mass of the cube.
i.e., a3ρ = N × \(\frac{M}{N_A}\)
∴ ρ = \(\frac{N\times M}{a^3\times N_A}\)