# Atomic mass number question

1. ### mawalker

53
sorry, i'm having trouble grasping a lot of this... i feel like i have a general understanding of what's going on but a lot of the problems are still confusing to me...

this problem

An element in its solid phase has mass density 1750 kg/m3 and number density 4.39 * 10^28 atoms/m3.

asks what is the element's atomic mass number

i thought that it should just be 4.39*10^28 divided by 1.661 *10^-27 = u, but then i'm not sure where the mass in kg comes in to play

2. ### Max Eilerson

122
1 au = 1.661 *10^-27 Kg.

3. ### mawalker

53
yeah, i know the atomic unit number but how does it relate to mass density?

4. ### mawalker

53
can anyone point me in the right direction? i'm still not getting this

5. ### quasar987

4,770
$$\rho=nm$$

where rho is the mass density, n is the number density and m is the mass of the atoms.