Download ChemCom Unit 1

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Per:
Date:
Lab Keeping an Eye on Ions
Purpose: To examine atomic models of ions and identify the element and net charge
Here is a simple atomic model of a beryllium atom. The nucleus, in the center, is made up of protons and neutrons.
Electrons occupy the space outside the nucleus. For now, we will only be concerned with the number of
electrons, and we will not worry about the arrangement of electrons around the nucleus.
2
He
4.0
1
H
1.0
3
Li
6.9
4
Be
9.0
5
B
10.8
6
C
12.0
7
N
14.0
8
O
16.0
9
F
19.0
10
Ne
20.2
11
Na
23.0
12
Mg
24.3
13
Al
27.0
14
Si
28.1
15
P
31.0
16
S
32.1
17
Cl
35.5
18
Ar
39.9
The number of protons determines the identity of the atom. From the partial periodic table above, how many
protons do you think beryllium has? Label the electrons, neutrons, and protons in the model above.
Each proton has a charge of +1. Each electron has a charge of -1. Neutrons have no charge. In a beryllium
atom, the charges add up like this:
proton charge
+4
electron charge
4
net charge
0
1. When an atom has an unequal number of protons and electrons, it has a net charge and becomes an ion. For
example, in the atom to the right, subatomic particles and their charges add up like this
proton charge
electron charge
+3
2
net charge
+1
Because there are three protons, it is a lithium atom. Because there are more protons than electrons, the
particle has an overall +1 charge; the ion is written like this: Li+ or Li1+. Under normal conditions, it is not
possible to change the number of protons in an atom, as the protons are buried in the nucleus. However, it is
possible to add or subtract electrons in an atom.
2. Identify the element shown, based on the number of protons: ______.
Add up the charge: proton charge
electron charge
_______
net charge
The ion is: __________.
3. Identify the ion shown, based on the number of protons and electrons: ________.
Add up the charge: proton charge
electron charge
net charge
________
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Procedure
1. Each bag, A-L, represents an atom. The atom may be neutral, a cation (+ charge) or an anion ( charge.)
2. The small inner bag represents the atomic nucleus, which has protons (red stones) and neutrons (clear
stones). The black beads represent electrons, which are outside the nucleus.
3. For each bag, record the number of protons, neutrons, and electrons. Record the element name, and the
element symbol.
4. Calculate the overall charge of the element represented. If it is an ion, write the proper ion symbol in the
data table.
Ions Report Sheet
Bag
# of
Protons
# of
Neutrons
# of
Electrons
Element Name
Element
Symbol
Ion
A
B
C
D
E
F
G
H
I
J
K
L
2
Analysis (Answer in full sentences)
1. How can you tell an atom’s identity (which element), given the number of protons, neutrons, and electrons.
2. What is the charge (positive, neutral, or negative) of the nucleus of every atom?
3. What is the charge (positive, neutral, or negative) on an electron?
4. Compare the mass of a proton with the mass of an electron.
5. Determine the charge of each of the following ions. The first one is done as a model.
a. Oxygen ion with 10 electrons
# protons = 8
# electrons = 10
net charge = 2
b. Phosphorus ions with 18 electrons
# protons =
# electrons =
net charge =
c. Calcium ion with 18 electrons
# protons =
# electrons =
net charge =
d. Bromine ion with 36 electrons
# protons =
# electrons =
net charge =
e. Calcium ion with 18 electrons
# protons =
# electrons =
net charge =
6. Determine the number of protons and electrons in each of the following ions. Hint: are there more protons
or electrons? How many more?
a. S2-
# protons =
# electrons =
b. Cu+
# protons =
# electrons =
c. Fe3+
# protons =
# electrons =
d. I-
# protons =
# electrons =
e. Ni2+
# protons =
# electrons =
f. Ag+
# protons =
# electrons =
g. H-
# protons =
# electrons =
h. Cr6+
# protons =
# electrons =
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