Prescriptive Activities: Facet Cluster 1.6: PF#70-73
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Prescriptive #70-73:
70 The student doesn't fully understand that electrostatic attractions form the basis of
bonding between atoms.
71 Student remembers the 'rules' for determining the formation of bond types, but does not
remember that it is the electrostatic attraction between two or more atoms that creates
bonds. e.g. "metals and nonmetals bond" rather than the outermost electron in a metal is
more attracted to the nucleus of an adjacent (nearby) nonmetal than its own metallic
nucleus.
72 The student thinks that an atom will spontaneously lose an electron.
73 The student thinks that an atom will 'grab' 'extra' electron(s) that exist by themselves in
space.
Materials:
Student handout
Magnets that can be stacked together – these represent protons
Metal ball – represents an electron
Lined paper or graph paper (optional)
Background
How electrons are pulled from way place to another
The atom is the simplest piece of an element and consists of protons and neutrons in the
nucleus with electrons outside the nucleus. When we talk about bonding between atoms we
often oversimplify things by stating the general rules for bonding, such as “metals and
nonmetals bond to form ionic compounds”. However, to really understand chemistry it is
necessary to know the underlying principles for these rules. In other words, why do a metal
and a nonmetal form an ionic bond? Why do two nonmetals form a covalent bond?
To get to the answer to this question, think about what holds electrons within an atom….
Electrostatic attraction is the attraction between oppositely charged particles. This is what
holds electrons within atoms. The positively charged protons in the nucleus attract the
negatively charged electrons.
The role of electrostatic attraction in bonding
When atoms bond, the nucleus of each atom is electrostatically attracted not only to its own
electrons, but also to the electrons of neighboring atoms.
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Ionic Bonding
Prescriptive Activities: Facet Cluster 1.6: PF#70-73
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The reason that “a metal and a nonmetal will form an ionic bond” together is because the
positively charged nucleus of the nonmetal is better able to attract the electrons towards
itself than the metal atom is. This attraction is actually strong enough to completely remove
the outermost valence electrons from the metal. Thus, the nonmetal gains electrons and
becomes a negatively charged ion, while the metal loses electrons and becomes a positively
charged ion. An ionic bond forms because the positively and negatively charged ions are
electrostatically attracted to each other. It is important to note that electrons do not simply
come off of an atom. In bonding, they are “pulled” off by another atom.
Ionic bonding
Covalent Bonding
The reason that “two nonmetals form a covalent bond” where they
share electrons is because neither atom has a strong enough “pull”
on the electrons to completely remove the outer electrons from the
other atom. The covalent bond is formed because both nuclei are
electrostatically attracted to the electrons from the other atom,
but neither one strongly enough to remove the electrons. The image
shown here represents two atoms, each with a single proton (+) and
a single electron. Notice that each electron is attracted to both
protons. The image also indicates the repulsion between like
charges that also factors into bonding.
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Prescriptive Activities: Facet Cluster 1.6: PF#70-73
Teacher Page
Misconceptions about electrons
1. When discussing the electron transport chain (ETC) in biology, we often depict free
electrons simply moving through the chain. It is a very complicated system and it is not
until studying this in great detail in college that students learn where those electrons
come from. It is important to understand that in each step of the ETC electrons are being
attracted by atoms that are able to remove the electron from its previous position. The
electrons do not just simply come off of an atom. They must be pulled off by the protons
in the nucleus of some other atom.
2. Another misconception can arise when studying
electricity and magnetism; we encounter electrons that
appear to be “on their own”, such as in the image
shown here. Again, the electrons are being pulled by
protons in the nucleus of other atoms. In this
illustration, those other atoms are simply represented
by the “+” on the battery.
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Prescriptive Activities: Facet Cluster 1.6: PF#70-73
Teacher Page
Directions for Activity:
1. Attach the metal ball to one magnet. The magnet represents a positively charged
proton and the metal ball represents a negatively charged electron. Place this on top
of a piece of graph paper or lined paper.
2. Now, slowly bring a second “proton” magnet close to the metal ball “electron”, and
see how close it gets before removing the “electron” from the “proton” magnet.
Record this distance by counting the number of lines on the paper between the
magnet and ball.
3. Now attach several magnets together to represent an atom with many protons in the
nucleus. Using this large “atom”, again slowly bring it towards the metal ball attached
to a single magnet. Record how close it can approach before removing the “electron”.
4. After exploring with the magnets and reading about the role of electrostatic
attraction in bonding, answer the questions at the end of the activity.
Questions:
1. Would the magnets ever spontaneously separate from each other (without an
outside force acting on them)?
2. What is the charge on a proton?
3. What is the charge on an electron?
4. How do the magnets and metal ball represent what is going on inside an atom?
5. What holds electrons within an atom?
6. Under normal conditions are there free electrons just roaming around?
7. Explain the underlying reason for the rule “metals and nonmetals form ionic bonds”.
8. Explain the reason for the rule “two nonmetals will form a covalent bond”.
Teacher Notes
Here’s an example of the magnets you can use in this activity.
References
Image of hydrogen atoms bonded:
http://www.chemistryland.com/CHM130W/11-Bonds/bonds.html
Electron Transport Chain image taken from:
http://fhs-bio-wiki.pbworks.com/w/page/12145766/ETC
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