Download of atoms. - Digital Chalkboard

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There are 92 naturally occurring kinds of atoms
found on Earth, each with a different number of
protons, electrons, and neutrons. The number of
Key Question
electrons in the outermost shell determines the chemi­
How can we make a model of .,n atom that shows its
cal properties of the atom. Each different kind of atom
is called an element and is identified by its atomic
electrons, protons, and neutrons?
number (the number of protons in the atom). Chem­
Learning Goal
ists also define an element as a simple substance that
Students will make simple models of atom.
cannot be broken down into any smaller component
by ordinary chemical reactions.
Protons and electrons have a property called
Guiding Document
Project 2061 Benchmarks
charge. All electric phenomena are caused by charges.
.. All mailer is made up of atoms, which are far too
By convention, protons are said to have a positive
small to see directly through a microscope. The
charge, and electrons a negative charge. Neutrons
have no charge. Most atoms have the same number
atoms of any element are alike but are different
from atoms ofother elements.
of protons and neutrons and are electrically balanced.
If an atom has different numbers of protons and elec­
• Models are often used to think about processes
[hat happen 100 slowly, too quickly, or on too
trons, it is called an ion. If there are more electrons
smail a scale to obserue direclly, or thaf are too
than protons, it is a negative ion. If there are more
uastto be changed deliberately, or that are poten­
protons than electrons, it is a positive ion.
tially dangerous.
It is impossible to picture atoms accurately; for
example, electrons have a dual nature and can take
Science
the form of both particles and waves. The only accu­ rate model of an atom is an abstract, mathematical
Physical science
one. Since this type of model does not help most
matter
atoms
people understand atoms, several other models
are usually used when describing atoms. The most
Integrated Processes
common is the Bohr model. It pictures a central mass
Observing
(nucleus) made up of protons and neutrons orbited
by electrons.
Comparing and contrasting
The Bohr model, like all non-mathematical ones,
Materials
has distortions of the size and space relationships
within an atom. It is difficult to accurately convey the
Per set of atoms:
vastness of the empty space within atoms. If an atom
construction paper
plastic bag of miniature marshmallows, 10 of each
were two miles in diameter; it would appear to be solid.
three different colors
since the electrons would be orbiting the outer shell
at 'almost the speed of light. Yet, its nucleus would
glue
only be about the size of a golf ball and its electrons
markers
the size of BBs; all the rest would be empty space.'
Background Information
The atom model used in this lesson is similar to
All matter is made up of atoms, which in turn are
the Bohr modeL While not very accurate. it does show
the basic parts of an atom and the atomic shells. It is
made up of smaller particles called protons, neutrons,
and electrons. Together, protons and neutrons form
intended to be a starting point for students in building
the central core, or nucleus, of an atom. Electrons,
their conceptualization of the atom.
which have only 1/1840 the mass of protons and
Management
neutrons, orbit the nude.us in layers called shells.
l. Students can work alone or in groups.
There are rules by ~hich the shells operate.ln,the
2. Plastic bags with the marshmallows should be
innermost shell near the nucleus, only two electrons,
made up ahead of time for individual groups.
can orbit. In the second shell. only eight can orbit.
3. Three colors of colored dots, colored cereal, or
Other shells beyond this can hold more electrons,
except for the outermost shell. which never has more
construction paper circles can be used instead of
than eight.
marshmallows to represent the protons, etectrons,
and neutrons.
Topic
Atomic structure
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ELECTRICAL CONNECTIONS
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4. Since electrons are SO much smaller than protons
and neutrons, smtsller bits of m;"rsrunallow, or smaller
colored dots can be used to represent them.
5. The activity sheet can be used to make models of
atoms if the other materials are not available.
Procedure
1. Students will make models of three different atoms.
Drawa diagram of an atom on the board and tell the
students that atoms are made up of three impor­
tant parts: the protons, neutrons, tsndthe electrons.
You may want to tell students about the charges on
protons (+) and electrons (-).
2. Explain that atoms are the building blocks of
matter and that they differ only in the number of
protons, electrons, and neutrons. Tell students
that the number of protons present (the atomic
number) determine what type of atom it will be.
For example, carbon has an atomic number of six.
It has six protons, six electrons, and usually six
neutrons.
3. Demonstrate how to make a model of an atom.
Using three different colors of marshmallows and
a piece of construction paper. construct a model
or a helium alom. Glue two "protons" (first color of
marshmallow) lind two ~neutrons" (second color)
together in the center of the "atom" to form the
nudeus. Draw a cirde (shell) around this nucleus
imd glue two "electrons~ (third color) somewhere
on the circle. Since the mass of the electrons
is much less than the mass of the protons and
neutrons, use small pieces of marshmallow to
represent each electron.
DISCUSS the fact that these marshmallow models
are only like real atoms in a few ways (they show
the'three main particles in atoms, they show the
nucleus made of protons and electrons, they show
the electrons as orbiting the nucleus in shells, they
show that electrons and protons have charge).
Explain thl:it models sometimes help us. under­
stand difficult concepts. Emphasize the fact that
real atoms are incredibly small and wondrous
things with many amazing properties.
Connecting Learning
I. How are all atoms the same? [They are made of
electrons, protons, and neutrons.J
2. What is at the center of every atom? [The nucleus,
which is made of protons and neUlTons.)
3. What orbits the nucleus? [electronsJ
4. How is the nucleus of the hydrogen atom dIffer­
ent from the nucleus of the helium atom? [The
hydrogen dtom does not have any neutrons in its
nucleus.J
5. How is the carbon atom different from the helium
atom? [It has electrons orbiting in two electron
shells J
6. What atomic particle is related to the \',ord elec­
tricity? {electron}
7. How could we build models of other aloms? [Use
different numbers of marshmallows. J
8. What are you wondering now?
Extensions
1. Use the actiVity sheet to make a model of an
oxygen alom (atomic number is eight).
2. Make models of other atoms. You will need more
than two shells for larger atoms.
3. Use other materials to make models of atoms.
4. Study the periodic tabie. Look at how the number
of electrons in the outer shell of an atom deter­
mines what family it is in.
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4. Distribute the marshmallows and construction
paper. Have students construct a hydrogen atom
(one proton, one electron), a helium ctom (two
protons, two neutrons, two electrons), and a
carbon atom (sIx protons, six neutrons, six elec­
trons). The first shell (inner circle) of the carbon
atom has two electrons, the second shell (outer
circle) will have four electrons.
5. Students may use markers to drctw the electron
shells. Markers can also be used to put a (+) on
each proton and a (-) on each electron.
6. Students will use the remaining three marshmal­
lows to make a key for their atom model (there will
be one extra "neutron" left over). For example, pink ;.
proton (+); green'" neutron: yellow", electron (-).
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ELECTRICAL CONNECTIONS
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Key Question
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How can we make a model
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make simple models
of atoms.
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Connecting Learning
1. How are all atoms the same?
2. What is a the center of every
atom?
3. What orbits the nucleus?
4. How is the nucleus of the hydrogen
atom different from the nucleus of
the helium atom?
5. How is the carbon atom different
from the helium atom?
6. What atomic particle is related to the
word electricity?
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7. How could we build models of other
atom?
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8. What are you wondering now?
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