the atomic volume per mole of yetterium is greater than lutetium. why?
The molar volume (the atomic volume per mole), symbol Vm is the volume occupied by one mole of a substance (chemical element or chemical compound) at a given temperature and pressure. It is equal to the molar mass (M) divided by the mass density (ρ). The molar volume of Ytterbium (atomic radius is 176 pm) is 24.84 • 10−6 m3/mol; The molar volume of Lutetium (atomic radius is 174 pm) is 17.78 • 10−6 m3/mol. The ionic radii of the lanthanides decrease from La to Lu in the lanthanide series. This effect is named "lanthanide contraction". The effect results from poor shielding of nuclear charge (nuclear attractive force on electrons) by 4f electrons; the 6s electrons are drawn towards the nucleus, thus resulting in a smaller atomic radius and molar volume.