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POGIL EXERCISE 04
Anatomy and Physiology of the Atom
Each member should assume his or her role at this time. The new manager takes charge of the POGIL
folder and hands out the GRF and RRF to the appropriate members. The new recorder should record
the names of the group members on the new GRF.
Table 1. Group Member Role Assignments
GROUP TYPE ->
MEMBER NO. ->
Manager
Reporter
Recorder
Reflector
Technician
Encourager
SFUC
1
GROUPS OF THREE
2
3
+
+
+
1
GROUPS OF FOUR
2
3
+
+
4
+
+
+
+
+
+
*
+
The manager should direct the group to read Observation I below and then direct the
group to begin processing with Item 1:
OBSERVATION I: The atom is the smallest unit of an element that still retains the
chemical and physical properties of that element; however, the atom is not the smallest
unit of matter. Atoms are made up of even smaller pieces of matter called subatomic
particles. There are three primary subatomic particles: protons, neutrons, and
electrons (Table 2). The protons and neutrons are located in the center of the space
occupied by the atom; this center area is referred to as the nucleus of the atom. The
electrons orbit the nucleus in a manner that is often simulated as a cloud in diagrams in
modern chemistry books– not in planar orbits often depicted in older texts. Physicists
and chemists have a particular type of code to quickly identify the exact number of
protons, electrons and neutrons in an atom. This code is deciphered for you by Figure I.
Table 2. Major Subatomic Particles and Their Properties and Atomic Locations
NAME
MASS (AMU*) CHARGE
LOCATION
DETERMINES
Electron
5.6 X 10-4
-1
Outside the nucleus
Chemical Reactivity
Neutron
1
0
Nucleus
Isotope
Proton
1
+1
Nucleus
The element
*Atomic Mass Unit (AMU) equals 1.7 x 10-24 grams
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Figure I. Standard Atomic Notation Format
*If this notation is not shown, the charge is zero.
**Often not written because it can be obtained from periodic chart.
1. What do the initials AMU stand for? ____________________ Why do you think this
special unit is used by chemists if the actual mass is known in grams?
2. What is the mass in grams of an electron? _______________________
3. According to Table 2, what two subatomic particles have the same mass?
______________________ ______________________
4. What conclusion can be drawn about the mass distribution in an atom?
5. The helium atom is composed of 2 protons, 2
neutrons and two electrons. Draw a modern
diagram of the atom in Figure II to the right
consistent with diagrams in Chapter 4 & 11 of the
text. Have instructor examine the diagram.
6. The atomic mass number (A) of an atom is the
mass of the atom in AMU to the nearest whole
number. What is the atomic mass number for
this helium atom? __________
7. Write an Equation (EQ1) below that would
calculate A of any element given the specific
number of major subatomic particles.
Figure II. Modern Diagram of
Helium Atom
EQ1: A =
Recorder should present the group’s work to instructor for validation.
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OBSERVATION II. The number of Protons in the nucleus determines the element to which
the atom belongs; the number of protons is referred to as the atom’s atomic number (Z). This
means that all atoms that have the same atomic number have the same chemical properties
and belong to the same element. However, all atoms of the same atomic number may not
have the same atomic mass number. This means that although they have the same number of
protons, they may have different number of neutrons and thus different atomic mass numbers.
Atoms that have the same atomic number but different atomic mass numbers are called
isotopes. You will recall that the nucleus of the atom contains all the protons and neutrons of
the atom; therefore, all most all of the mass and all of the positive charge resides in the center
of the atom. The function of the neutrons is believed to be that they prevent the nucleus from
flying apart due to the repulsion of like charges. Evidence for this proposal is that the larger
the atomic number the higher the ratio of neutrons to protons.
8. What is the charge associated with the nucleus? ___________
9. Using the information in Observations I and II, the periodic table at the end of this
exercise, and Row 1 of Table 3, fill in the blank cells of Table 3.
Table 3. Comparison of Atomic Mass to Ratio of Neutrons to Protons
ELEMENT
Number of
Number of
Name
Symbol
Neutrons (N)
Protons (Z)
2
2
Helium-4
4He
N
P
1.00
.
2
20Ne
10
Argon-40
84Kr
36
Xenon-131
Radon-222
Recorders should present Table 3 to the instructor for validation.
10. Plot in Figure III the values of N/P for neon through radon calculated in Table 3.
Draw the best straight line through the points using a straight edge.
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Figure 3. Relationship of Neutrons to Protons as Atomic Mass Increases
11. Do the data in Table III and Figure III support the observation made in the first part
of Observation II concerning the relationship between protons and neutrons? _____
Explain your answer:
Recorders should present their diagram to the instructor for validation before the group
continues processing by reading Observation III.
OBSERVATION III. The number of electrons in the atom determines the charge of the atom.
The charge of an atom (C) is equal to the number of protons minus the number of electrons.
Elemental atoms have a charge of zero because in the elemental form the number of protons
and electrons are equal. However, in a chemical reaction electrons are either donated and
accepted or shared between the elemental atoms involved in the reaction. In the case where
electrons are donated and accepted the atom becomes charged; a charged atom is called an
ion. When an atom gains electrons, it becomes negatively charged and is called an anion.
When an atom loses electrons, it becomes positively charged and is called a cation. One more
concept about electrons you should know: the arrangement of the electrons around the
nucleus determines the chemical properties of the element. This will be directly covered in a
future POGIL; moreover, everything else in chemistry is related to the electron arrangement.
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12. Write a mathematical expression (Equation 2) that can be used to calculate the
charge (C) of any atomic species.
EQ2: C =
13.Using information from the periodic table at the end of this exercise, Observation III
and Row 1 of Table 4, fill-in the values for the blank cells in Table 4.
Table 4. Determining the Type and Charge of Various Atomic Species
Atomic Species
Number of Number of
Charge
Classification**
Protons
Electrons
Name*
Symbol
Chloride-36 ion
36
17
Cl-
17
18
-1
anion
Silver-108
28
Si
14
Oxide-16 ion
-2
31
P
15
*All ion names must include the word, ion, in the name as shown in Row 1. In addition, anion first
name is formed by using the elemental stem + ide as shown in Row 1. The cation’s first name is
just the name of the element; e.g., Cs+ is named the cesium ion.
**Classify as either an atom (E), cation (C), or anion (A).
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14. Using the information gathered from all previous sections, complete Table 5.
Table 5. Basic Properties of Selected Atomic Species.
ROW
Species
Symbol Number Number
Name
Protons Neutrons
1
Chloride-36 ion
Atomic
Mass
Number
Electrons
Charge
36
18
-1
36
Cl-
17
19
17
+1
2
Sodium-23 ion
3
1
4
1
0
1
2
1
8
14
0
36
0
5
12C
6
7
8
17
23Na
Recorders should present the group’s Table 3 to the instructor for validation. Managers
should resume processing once the results have been verified.
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15. Isotopes of an element have the same atomic number but different atomic masses.
List below the atomic species in Table 5 that are isotopes. List them by symbols in
their elemental groups.
16. How do you know from the name of the species whether it is charged or not?
18. How do you know from the name of an atomic species whether or not it is
negatively charged?
19. How do you know from the name of an atomic species whether or not it is positively
charged?
EXERCISE END. Managers should collect the GRF, the Recorders exercise and the RRF,
paperclip them together, and place in the left pocket of the folder. The folder should
be closed and left on the table.
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