In the periodic table, the atomic radius decreases as we move from left to right in a period. However, the atomic volume should also decrease as a result of the decrease in atomic radius, as volume is given by $\frac43\pi r^3$. Instead, the atomic volume initially decreases upto group 14 and then increases, as is shown by the Lothar Meyer curve:
I am aware that the atomic volume is given by gram atomic mass divided by density. However, these form two contradictory theories - according to the Lothar Meyer curve, should atomic radius not follow the same behaviour? Or conversely, according to the measurement of atomic radius, should the Lothar Meyer curve and atomic volume not decrease across a period?