Avogadro, Amedeo << `ah` vuh GAH droh, `ah` mah DEE oh >> (1776-1856), was an Italian physicist. He proposed in 1811 his famous hypothesis, now known as Avogadro’s law. The law stated that equal volumes of all gases at the same temperature and pressure contain the same number of chemical units. Avogadro distinguished between gases composed of complex units (molecules) and gases made up of simple units (atoms). He was able to calculate from gas densities the amount of matter in atoms and molecules (see Atom (Relative atomic mass) ). The leading scientists of Avogadro’s time rejected his hypothesis until 1858, when the Italian chemist Stanislao Cannizzaro reintroduced it and developed it further.
Avogadro also introduced a basic unit of quantity in chemistry called a mole (see Mole ). Still widely used today, a mole contains 6.022137 x 1023 atoms or molecules of a single type of substance. This quantity is referred to as Avogadro’s number. Avogadro was born in Turin, Italy, on Aug. 9, 1776. He died on July 9, 1856. See also Chemistry (Development of physical chemistry) .
