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Conceptual Chemistry
PRACTICE PAGE
Chapter 4: Subatomic Particles
Subatomic Particles
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Conceptual Chemistry
PRACTICE PAGE
Chapter 4: Subatomic Particles
Drawing Shells
Shells can be represented by a series of concentric circles, as shown in Figure 4.26 of your
textbook. With a little effort, however, it’s possible to show these shells in three dimensions.
Grab a pencil and blank sheet of paper and follow the steps shown below. Practice makes
perfect.
1. Lightly draw a diagonal guideline. Then, draw a series of seven semicircles. Note how the
ends of the semicircles are not perpendicular to the guideline. Instead, they are parallel to
the length of the page, as shown in Figure A.
Figure A
Figure B
2. Connect the ends of each semicircle with another semicircle such that a series of concentric
hearts is drawn. The ends of these new semicircles should be drawn perpendicular to the
ends of the previously drawn semicircles, as shown in Figure B.
3. Now the hard part. Draw a portion of a circle that connects the apex of the largest vertical and
horizontal semicircles as in Figure C.
Figure C
Figure D
4. Now the fun part. Erase the pencil guideline drawn in step 1, then add the internal lines, as
shown in Figure D, that create a series of concentric shells.
You need not draw all the shells for each atom. Oxygen, for example, is nicely represented
drawing only the first two inner shells, which are the only ones that contain electrons. Remember
that these shells are not to be taken literally. Rather they are a highly simplified view of how
electrons tend to organize themselves within an atom.
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Conceptual Chemistry
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Chapter 4: Subatomic Particles
Atomic Size
1. Complete the shells for the following atoms using arrows to represent electrons.
2. Neon, Ne, has many more electrons than lithium, Li, yet it is a much smaller atom. Why?
3. Draw the shell model for a sodium atom, Na (atomic number 11), adjacent to the neon atom in the
box shown below. Use a pencil because you may need to erase.
a. Which should be larger: neon’s first shell or
sodium’s first shell? Why? Did you
represent this accurately within your
drawing?
b. Which has a greater nuclear charge, Ne or Na?
c. Which is a larger atom, Ne or Na?
4. Moving from left to right across the periodic table, what happens to the nuclear charge within
atoms? What happens to atomic size?
5. Moving from top to bottom down the periodic table, what happens to the number of occupied
shells? What happens to atomic size?
6. Where in the periodic table are the smallest atoms found? Where are the largest atoms found?
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Conceptual Chemistry
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Chapter 4: Subatomic Particles
Effective Nuclear Charge
The magnitude of the nuclear charge sensed by an orbiting electron
depends upon several factors, including the number of positively
charged protons in the nucleus, the number of inner-shell electrons
shielding it from the nucleus, and its distance from the nucleus.
1. Place the proper number of electrons in each shell for carbon and silicon (use arrows to
represent electrons).
2. According to the shell model, which should experience the greater effective nuclear charge:
an electron in
a. carbon’s first shell or silicon’s first shell?
b. carbon’s second shell or silicon’s second shell?
c. carbon’s second shell or silicon’s third shell?
(circle one)
(circle one)
(circle one)
3. List the shells of carbon and silicon in order of decreasing effective nuclear charge.
>
>
>
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4. Which should have the greater ionization energy, the carbon atom or the silicon atom?
Defend your answer.
5. How many additional electrons are able to fit in the outermost shell of
carbon?
silicon?
6. Which should be stronger, a C–H bond or an Si–H bond?
Defend your answer.
7. Which should be larger in size: the ion C
Why?
4+
4+
or the ion Si ?