## College Physics (4th Edition)

A helium atom consists of 1 proton and 1 neutron. The mass of one helium atom is $2~u$ We know that 1 mole of helium has a mass of $2~g$. We can find the number of moles in $13~g$ of helium: $\frac{13~g}{2~g/mol} = 6.5~mol$ There are 6.5 moles of helium in 13 grams of helium.