 Due to the lanthanide, actinide, and superactinide contractions, unhexquadium should have a metallic radius of only 158 pm, very close to that of the much lighter magnesium, despite its expected atomic weight of around 474 u which is about 19.5 times the atomic weight of magnesium.This small radius and high weight cause it to be expected to have an extremely high density of around 46 g·cm−3, over twice that of osmium, currently the most dense element known, at 22.61 g·cm−3; unhexquadium should be the second most dense element in the first 172 elements in the periodic table, with only its neighbor unhextrium (element 163) being more dense (at 47 g·cm−3).Metallic unhexquadium should have a very large cohesive energy (enthalpy of crystallization) due to its covalent bonds, most probably resulting in a high melting point.