Uranium hexafluoride is a solid at room temperature, but it boils at 56°c. determine the density of uranium hexafluoride at 73°c at 763 torr.

                    Density  =  12.40 g/L       (or)    0.01240 g/mL

Data Given;

                 Pressure  =  P  =  763 torr   =   1.00395 atm

                 Temperature  =  T  =  73 °C + 273.15  =  346.15 K

                 M.mass of UF₆  =  M  =  352.02 g/mol

                 Gas Constant  =  R  =  0.0821 atm.L.mol⁻¹.K⁻¹

Formula Used,

                     Density  =  P M / R T

Putting values,

Density  =  (1.00395 atm × 352.02 g.mol⁻¹) ÷ (0.0821 atm.L.mol⁻¹.K⁻¹ × 346.15 K)

Density  =  12.40 g/L   (or)    0.01240 g/mL

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.