Urban Teaching Resources: © Shawn Urban 29/02/12. CC BY-NC-SA 3.0

Page for Teachers and Discussion
•• Page for Students and Presentation ••

Twelve Lead Pencils The size of an atom and the number of atoms in Space are hard to visualize. This analogy makes these concepts more concrete.

Some Initial Concepts

How large is an atom? How many atoms are in the leads of 12 lead pencils?

Twelve pencil leads weigh approximately 12 grams, so have 6.02 x 1023 atoms in them.



But what does 6.02 x 1023 atoms mean?

Green Pea Analogy

ExponentValueAnalogy
100  1  One pea
101  10  10 peas - spoonful
102  100  10 spoonfuls of peas - plateful
103  1000  10 platefuls of peas - bag
104  10 000  10 bags of peas
105  100 000  100 bags of peas - fridgeful
106  1 000 000  10 fridgefuls of peas - an average bedroom
107  10 000 000  Average house full from basement to attic with peas
109  1 000 000 000  100 houses full from basement to attic with peas - a small village
1012  1 000 000 000 000  100 000 houses full from basement to attic with peas - a small city
1015  1 000 000 000 000 000  A large city like New York covered 1 m deep with peas
1018  1 000 000 000 000 000 000  A province like Alberta covered 1 m deep with peas
1020  100 000 000 000 000 000 000  The land mass of Canada covered 1 m deep with peas
1021  1 000 000 000 000 000 000 000  The land mass of the world covered 1 m deep with peas
1023  100 000 000 000 000 000 000 000  The entire surface of the earth plus 99 planets just like earth covered 1 m deep with peas
6.02 x 1023  602 000 000 000 000 000 000 000  602 planets like earth covered 1 m deep with peas = 12 pencil leads = one mole of carbon atoms = 1/18 the surface area of the Sun

You may be interested in a Slideshare Presentation created by Pak Liam in response to this table. The Slideshare is part of Pak's science resources page of his blog.

Summary Concepts

For More Information on Atoms

I created a related page, The Elements, about the Periodic Table. If you are looking for the links I had on this Analogy page, this is where they went. This page has many links useful to introductory element chemistry.

I also wrote a post, About Atoms and Mole Hills, in my blog, Digital Substitute, about using this analogy. It also contains links with explanations about atoms, moles, elements and the periodic table.

For an explanation of the naming of the value of Avogadro's Number, see Names for Large Numbers.



This file created by Shawn Urban and last updated on 29/02/12. This analogy is taught in junior and senior highs to make the notions of atom size and atom quantity more concrete. The analogy is widely used; its initial source is unknown. Credit for the Green Pea Analogy goes to established teacher use.