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Developmental Lesson FC #1.3:
Bean Counting
Teacher Notes and Materials
1.3: Elements
Goal Facets:
01 The student understands that in every atom that makes up one kind of element, the number
of protons is the same, but the number of neutrons or electrons may vary.
02 The student understands that all substances come from a limited number of elements in our
universe.
03 The student knows that the nucleus of an atom does not change easily, which explains why
we cannot easily make one element from another element.
04 The student knows that an atom's identity remains the same regardless of the state of matter
or the type of matter of which it is a part.
Background
The entire universe consists of only a limited number of elements which make up
everything that we experience in our daily lives as well as the stars and galaxies which shine
millions of light-years away. An atom of a particular element can be identified by the number
of protons in its nucleus. For example, if an atom has 11 protons it is a sodium atom. If the
number of protons is not 11, then it is not sodium. For any given element, the number of
neutrons or electrons may vary without altering the identity of the element. For example, one
fluorine atom may have 9 protons and 9 neutrons while another fluorine atom may have 9
protons and 10 neutrons. These are said to be two different isotopes of fluorine. Isotopes are
atoms of an element with different numbers of neutrons.
Atoms of one element don’t easily change into atoms of another element. However,
they may gain or lose electrons to become ions. An atom of fluorine may gain an electron from
some other atom, in which case it would now have a charge of -1. Even though it has gained an
electron, it is still fluorine because the number of protons has not changed.
Materials:
 Student handout
 Beans (2 distinct types)
Procedure:
Considering the following substances and their chemical formulas:
1. Liquid water, H2O
2. Ice, H2O
3. Water vapor, H2O
4. Diamond, C
5. Graphite, C
6. Carbon dioxide gas, CO2
7. Sucrose (sugar), C12H22O11
Developmental Lesson FC #1.3:
Bean Counting
Teacher Notes and Materials
From the beans provided, choose one kind to represent protons and another to represent
neutrons. Place the appropriate numbers of each kind of bean in the boxes below to represent
the elements indicated.
Liquid water, H2O
Hydrogen
Oxygen
Ice, H2O
Hydrogen
Oxygen
Water vapor, H2O
Hydrogen
Oxygen
Diamond, C
Carbon
Graphite, C
Carbon
Carbon dioxide gas, CO2
Carbon
Oxygen
Developmental Lesson FC #1.3:
Bean Counting
Teacher Notes and Materials
Carbon
Sucrose, C12H22O11
Hydrogen
Oxygen
Discussion Questions
1. Which subatomic particle determines the identity of an atom?
2. How did you decide how many neutrons to put in each box?
3. Does the atom change when it is a part of a different state of matter (solid, liquid, gas)?
4. Does the atom change when it is part of a different compound (e.g. carbon in carbon
dioxide versus sucrose)?
5. How many different elements make up the seven substances examined in this activity?
6. Look at the Periodic Table of the Elements. How many elements are there?
7. Do you think it is possible for other elements to exist? How would they be different
than those on the periodic table?
Developmental Lesson FC #1.3:
Bean Counting
Teacher Notes and Materials
Teacher Notes:
In this activity students will play with the roles of protons and electrons within atoms to study
the concepts of attraction to the nucleus, how the number of energy levels affects the size of
the atom, ionization energy and bonding.
Before doing the activity students will need to know how to determine the number of protons
and neutrons in an atom from the periodic table.
On the periodic table the atomic number tells you how many protons are in an atom of
an element. For example, Aluminum has an atomic number of 13 and therefore has 13
protons.
To find the number of neutrons you subtract the number of protons from the mass
number. On the periodic table, you can round the atomic mass to the nearest whole
number and use that value as the mass number.
You can also teach about percent abundances and atomic mass, but this is not necessary for
successful performance in the activity.
The atomic mass of an element is the weighted average of the naturally occurring
isotopes of an element. For example, iron exists as four naturally occurring isotopes
with the following abundances:
Isotope Atomic mass Percent
(amu)
abundance
Fe-54
53.9396
5.84%
Fe-56
55.9349
91.75%
Fe-57
56.93539
2.12%
Fe-58
57.93328
0.282%
To find the average atomic mass of an element, multiply the atomic mass of each
isotope by its percent abundance, expressed as a decimal, and add all of these values
together.
(53.9396 x 0.0584) + (55.9349 x 0.9175) + (56.93539 x 0.0212) + (57.93328 x
0.00282) = 3.1501 + 51.3203 + 1.2070 + 0.1634 = 55.84 amu
Remind the students that the atomic mass is determined almost entirely by the mass of the
protons and neutrons, as the mass of an electron is approximately 1/1800 the mass of a proton
or neutron.
Questions number 7 asks students to look at the periodic table and tell how many elements
there are. Their answer will depend on the date the table was created. You can address this by
Developmental Lesson FC #1.3:
Bean Counting
Teacher Notes and Materials
explaining the difference between the naturally occurring elements and the man-made
elements.
There are 92 elements which occur naturally on earth – all those up to # 94 (Uranium) except
for #43 (Technetium) and #61 (Promethium).
Technetium has not been found on earth. It has been produced in the lab and has been detected
in the spectra of stars other than the sun.
All of the Promethium that was originally present when the earth formed has disappeared due
to radioactive decay. Promethium occurs only in small trace amounts in uranium ores as a
fission product. Its longest-lived isotope has a half-life of 17.7 years.
Elements with atomic numbers of 95 to 118 have been synthesized. This is done in particle
accelerators and requires huge amounts of energy – far more than can be supplied by ordinary
chemical reactions.
References:
Steam image taken from:
http://en.wikipedia.org/wiki/File:Steam_Phase_eruption_of_Castle_geyser_with_double_rainb
ow.jpg
Diamond image taken from:
http://topforeignstocks.com/wp-content/uploads/2010/06/diamond.jpg
Carbon dioxide image taken from:
http://www.scienceclarified.com/Ca-Ch/Carbon-Dioxide.html
Sugar image taken from:
http://brooklynimbecile.files.wordpress.com/2010/03/refined_sugar-137163701.jpg