The electrons of a smaller atom or ion are the nucleus and held tightly than those of a larger atom or ion. A smaller atom or ion is therefore polarizable than a larger one.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3