Most of us are very familiar with the top four names and numbers, which occur in everyday life. What is the Mole and Avogadro's Number? Did you know that we are carrying quite a few Moles of substances in our bodies everyday. For a 200 Lb.(90 Kg.) person, the body holds, ignoring trace elements, about:

So, what is a Mole? A mole is the number of objects equal to the number of atoms in 12.0000 grams of carbon. It is also the gram- formula weight of a substance.

That number is equal to Avogadro's Number. How big is this number?

The Immensity of Avogadro's Number

Avogadro's Number is an immense number. How big is this number?

Here are a few estimates:

If you count out loud starting with the number "one" at the rate of one count every second, it may take you about 1,909,577,942,668,696 years to finish. This is roughly 960,000 times the estimated lifetime of our universe (assuming 20 Billion years).

Using a Pentium 450 MHz CPU, it will still take about 4,243,506 years to finish this task. This is a period of time about a thousand times longer than the total span of our civilization.

If marbles that have a diameter of one centimeter were to be lined up end-to-end in a straight line, the distance covered by this string of marbles can hold in about 500,000,000 of our Solar System placed end-to-end.

If we can't quite count that high in the human life span, can we estimate its value?

Avogadro's Number - The Race for Digits

Amadeo Avogadro proposed, in 1811, that equal volumes of gas contains an equal number of atoms or molecules, if the two volumes are held at the same temperature and pressure. This proposal became known as "Avogadro's Hypothesis". Even if Avogadro did not determine a numerical value for the number attributed to him, he has nevertheless planted the "seed" for it.

The first determination for the value of Avogadro's Number was made by Robert Brown (known for "Brownian" motion) in 1827.

Stanislao Cannizarro, in 1860, used Avogadro's Hypothesis as the basis for establishing a reasonable set of atomic weights for a number of elements. These atomic weights were used to obtain more accurate values for Avogadro's Number.

Robert Millikan (1923 Nobel Prize for Physics) performed his famous oil drop experiments in the 1920's. His work helped to establish a value of Avogadro's Number with improved accuracy that was cited by most chemistry textbooks into the early 1970's.

The table samples the numerical value for Avogadro's Number through the years to trace the quest for more digits and accuracy for the number. It is a miniature version of the quest for digits for the transcental number: PI.