# Iridium atom radius

The very dense metal iridium has a face-centered cubic unit cell and a density of 22.56 g/cm3. Use this information to calculate the radius of an atom of the element.

Please provide detailed explanation.

Thanks!

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#### Solution Preview

The radius of an atom can be calculated using the crystal lattice information and density. Ir has fcc lattice. This means that there are 4 atoms of Ir in one unit cell. So the density corresponds to the weight of 4 atoms of Ir that occupies the volume of a unit cell. Fcc lattice unit cells are cubes.

The volume of a cube = a^3. Now for fcc, the cell edge 'a' is related to the radius of the atom 'r' by the ...

#### Solution Summary

The radius of a face-centered cube is calculated from given data.

$2.19