Avogadro, Lorenzo Romano Amedeo Carlo
The Italian Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto (1776 - 1856), born to a noble family, was a scientist.
He formulated Avogadro's law stating that the ratio between the masses of the same volume of two gases (at the same temperature and pressure) corresponds to the ratio between their respective molecular weights. He clearly stated that gases are composed of molecules, and these molecules are composed of atoms.
He made a clear distiction between mass and weight.
He lent his name to Avogadro's constant NA = 6.022,140,76·1023 elementary entities of matter. The value of this constant, though not yet known by that name, was first obtained indirectly in 1865 by the Austrian physicist and chemist Johann Josef Loschmidt.