How large is an atom? How many atoms are in the leads of 12 lead pencils? Pencil leads are made of carbon atoms. Carbon has an atomic mass of 12. how can we visual this ?

1. Green Pea Analogy
Some Initial Concepts
How large is an atom? How many atoms are in the leads of 12 lead pencils?
Pencil leads are made of carbon atoms. Carbon has an atomic mass of 12.
Atomic mass is the mass of an atom. It is calculated as the sum of the number of protons and neutrons in the
atom, because protons and neutrons make up the majority of the atom's mass. Each proton and neutron is given
an atomic mass of 1. Since carbon has six protons and six neutrons, its atomic mass is 12. Carbon also has six
electrons, but these are extremely light compared to the protons and neutrons and do not contribute to
carbon's integral atomic mass.
Atomic mass is so light (1 atomic mass unit (amu) ∼ 1.66 x 10-24 g) that it is impractical to measure.
Instead, scientists estimate atomic mass by measuring the mass of the element (in grams) which is equal in
value to the number of protons and neutrons in an atom of the element. The amount of an element with this
mass (in grams) is called a mole. An atom of carbon has an atomic mass of 12, so a mole of carbon weighs 12
grams. Placing 12 grams of carbon (pencil lead) beside 28 grams of silicon (sand) enables one to visually contrast
the atomic mass of carbon (atomic mass 12) to that of silicon (atomic mass 28). (The comparison is not entirely
visual, since element density influences the volume of a mole of an element.)
A mole of any element contains 602, 000, 000, 000, 000, 000, 000, 000 atoms of that element, that is 602
sexillion US, 602 trilliard UK or 6.02 x 1023 atoms. This number is called Avogadro's Number after Amedeo
Avogadro (1776-1858) who discovered this number-of-atoms-in-a-mole relationship.
What does this have to do with 12 pencil leads?
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?

2. 100 = 1
One pea

3. 101 = 10
10 peas - spoonful

4. 102 =100
10 spoonfuls of peas - plateful

5. 103 = 1000
10 platefuls of peas – a bag

6. 104 = 10 000
10 bags of peas

7. 105 = 100 000
100 bags of peas - fridgeful

8. 106 = 1 000 000
10 fridges full of peas - an average bedroom

9. 107 = 10 000 000
Average house full from basement to attic with peas

10. 109 = 1 000 000 000
100 houses full from basement to attic with peas
- a small village

11. 1012 = 1 000 000 000 000
100 000 houses full from basement to attic with peas - a small city

12. 1015 = 1 000 000 000 000 000
A large city like New York covered 1 m deep with peas

13. 1018 = 1 000 000 000 000 000 000
A area like Kalimantan covered 1 m deep with peas

14. 1020 = 100 000 000 000 000 000 000
The land mass of China covered 1 m deep with peas

15. 1021 = 1 000 000 000 000 000 000 000
The land mass of the world covered 1 m deep with peas

16. 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

17. 6.02 x 1023
= 602 000 000 000 000 000 000 000
= 602 earth
sized planets = 12 = one mole = 1/18 the surface
covered 1 m pencil of carbon area of the Sun
deep with
leads atoms
peas