Answer:
1.31x10¹¹ g/cm³
Explanation:
The mass of the proton is equal to the mass of the neutron, which is 1.67x10⁻²⁴ g, so the mass of the alpha particle is 4*1.67x10⁻²⁴ = 6.68x10⁻²⁴ g.
1 fm = 1.0x10⁻²³ cm, thus the radius of the alpha particle is 2.3x10⁻¹² cm. If the particle is a sphere, the volume of it is:
V = (4/3)*π*r³, where r is the radius, so:
V = (4/3)*π*(2.3x10⁻¹²)³
V = 5.1x10⁻³⁵ cm³
The density of the particle is the how mass exists per unit of volume, so, it's the mass divided by the volume:
d = 6.68x10⁻²⁴/5.1x10⁻³⁵
d = 1.31x10¹¹ g/cm³
