CHEM 1701 – Lab 4 – Ions and Periodic Trends
Chemistry I for Pre-Health Sciences (online)
____/36 marks (6% of final grade)
Rationale
The purpose of this lab is to build representations of the imbalance in protons and electrons in ions, assign
IUPAC nomenclature to a variety of ion types, review periodic trends and explore applications of ions in
healthcare.
Learning objectives
The following learning objectives are covered in this lab.
CLO 6: Prepare for and conduct laboratory experiments to investigate scientific questions using
appropriate techniques.
CLO 7: Examine the relationships between chemistry and the health of the human
body.
LO 2.14: Recognize periodic trends of elements and use the trend to predict selected
properties of the elements.
LO 3.6: Apply IUPAC rules to name monatomic, multivalent and polyatomic
ions
LO 4.3: State the electronegativity trends on the periodic table and relate this
to electronegativity values
Procedure & Observations
Be sure to review the lab in its entirety before beginning.
Throughout the lab you are required to photograph parts of your experiment and include these photos
in your final submission.
Handing in your lab
When complete, submit your work to the appropriate folder in DC Connect under Assignments.
All materials needed throughout this lab:
20 small objects of one kind (i.e. raisins, beads, coins, tacks, cereal)
20 small objects of a second kind (i.e. dried beans, beads, Halloween candy)
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Experiment 1 – Flame Tests [8 marks]
Discovery question: Have you ever attended a fireworks display for Canada day and wondered how the
different colors light up the night sky? The answer: chemistry! In this experiment you will investigate some of
the colors made by the ions of different metals.
Watch it – Flame Tests [4:48]
This is a video of a process called flame tests. A sample of each ion is placed on the end of a wire and the wire
inserted into a flame. As you will see in the video, the different ions produce different colored flames. This is
the basis of how fireworks work.
Video link: https://youtu.be/NEUbBAGw14k
Observations
1. [1 mark colors + 7 marks names = 8 marks] Which color was produced for each of the following
metal cations? Provide the IUPAC name for each ion. [TIP: don’t forget to include “ion” in the name]
Metal cations Flame color IUPAC ion name
Li+ Pink Lithium Ion
Na+ Yellow Sodium Ion
K+ Lavender Potassium Ion
Ca2+ Red/Orange Calcium Ion
Sr2+ Red/Orange Strontium Ion
Ba2+ Yellow/Green Barium Ion
Cu2+ Blue/Green Copper (ll) Ion
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Experiment 2 – Visualizing Ions [7 marks]
Discovery question: In a neutral atom, the balance of positive and negative charge is equal. There are the
same number of protons and electrons. In an ion, there is an imbalance of positive and negative charge. How
can we demonstrate this imbalance visually?
Materials
20 small objects of one kind
20 small objects of a second kind
Procedure and Observations
1. [1 mark] Create a legend for your ions by identifying what object will represent each subatomic particle.
Protons Electrons
Blueberries
Popcorn
2. [6 marks] Use your chosen objects to visualize each of the following ions. Select the
appropriate ratio of protons to electrons that would result in the following ions. Photograph each of your
proportions and include the images in the spaces below.
Al3+ Oxide ion Calcium ion
Chloride ion P3- Potassium ion
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Experiment 3 – Periodic Trends [14 marks]
Access to a printer to print the graphs in experiment 3 OR
o you can use the line function (insert shapes) in WORD to create the lines on the graph
o if you do not have access to a printer you can create the graphs by hand using graph paper
o if you are really tech savvy you can create your graphs digitally using software like Excel
Discovery Question: The periodic table displays trends in atomic radius and ionization energy. How can we
summarize these trends in a visual way and interpret the data?
Materials
data table provided below
graphs provided below
Procedure
1. The atomic radius and ionization energy for the first 20 elements are shown in table 1 below.
2. Use the data to create two graphs:
i) Graph 1: Atomic Radius vs. Atomic Number
ii) Graph 2: Ionization Energy vs. Atomic Number
3. Plot the required points on each graph paper provided. Then, connect each of the points with a line.
Video: How to Plot Points on a Graph [5:38]
If you are unsure how to plot points on a graph, you may find this short video helpful. For the
graphs used in this lab I have provided you with the x-axis and y-axis labels as well as the
scale so you do not need to add these pieces to your graph. This means you can watch the
video from 4:15-4:50. [We are not using a “line of fit” in our graphs].
Video link: https://youtu.be/GUYRMdcEs00
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Use the following data for your graphs.
Table 1: Atomic Radius and Ionization Energy
A B C
Atomic Radius Ionization Energy
Element Atomic Number
(x10-12 m) (kJ/mol)
1 37 1,312
Hydrogen
Helium 2 32 2,372
Lithium 3 152 519
Beryllium 4 111 900
Boron 5 88 799
Carbon 6 77 1,088
Nitrogen 7 70 1,406
Oxygen 8 66 1,314
Fluorine 9 64 1,682
Neon 10 70 2,080
Sodium 11 186 498
Magnesium 12 160 736
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Aluminum 13 143 577
Silicon 14 117 787
Phosphorus 15 110 1,063
Sulphur 16 104 1,000
Chlorine 17 99 1,255
Argon 18 94 1,519
Potassium 19 231 418
Calcium 20 197 590
Graph 1 – Atomic Radius vs. Atomic Number
2. [2 marks] Use the data in table 1 to create graph of atomic radius vs. atomic number. Do this by using the
data in column A for the x-axis and data in column B for the y-axis. Once all of the points are
plotted, connect each point to the next with a line.
250
(x10-12 m)Atomic radius
200
150
100
50
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Atomic Number
Photograph your graph and insert the photo in the space below.
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Questions
3. [2 marks] What happens to the atomic radius between elements 2 and 3? Is this same relationship
observed between other elements? If yes, identify which elements.
The atomic radius between hemlium and lithium increases. This also happens with neon and
sodium and argon and potassium.
4. [2 marks] What happens to the atomic radius between elements 11 and 18? Is this same relationship
observed between other elements? If yes, identify which elements.
The atomic radius decreases between elements 11 and 18. This also happens with elements
berylium, boron, carbon, nitrogen, oxygen, fluorine, and neon.
5. [1 mark] Summarize the overall trend observed for atomic radius. Comment specifically on the trend seen
as you move across a period and down a group.
As you move across a period from left to right the trend for atomic radius seems to slowly
decrease until you come across elements 11 and 19. When moving down a group the trend for
atomic radius starts to increase.
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Graph 2 – Ionization Energy vs. Atomic Number
6. [2 marks] Use the data in table 1 to create graph of ionization energy vs. atomic number. Do this by using
the data in column A for the x-axis and data in column C for the y-axis. Once all of the points are plotted,
connect each point to the next with a line.
250
0
(kJ/mol)Ionization Energy
200
0
150
0
100
0
500
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Atomic Number
Photograph your graph and insert the photo in the space below.
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Questions
7. [4 marks] Which elements have the highest ionization energy? Are these elements in the same group?
Which elements have the lowest ionization energy? Are these elements in the same group?
Helium, neon, and argon have the highest ionization energy. Yes, these
Highest ionization energy elements are in the same group.
Lithium, sodium, and potassium have the lowest ionization energy. Yes,
Lowest ionization energy these elements are in the same group.
8. [1 mark] Summarize the overall trend observed for ionization energy. Comment specifically on the trend
seen as you move across a period and down a group.
As you move across a period from left to right the trend of ionzation energy seems to increase.
As you move down a group the trend seems to decrease.
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Experiment 3 – Health Applications [7 marks]
Discovery question: As a future healthcare worker you may come across cases of dehydration in children
and adults. There are many causes of dehydration including flu, food poisoning, heat and others. Sometimes
cases of dehydration are minor, other times they are more serious as is seen in cases of severe and prolonged
diarrhea. One treatment for diarrhea is liquid electrolytes. What are electrolytes and which ones are important
in the body?
Procedure
1. Visit this website to learn more about a common over the counter treatment for dehydration:
https://pedialyte.ca/en/dehydration-symptoms-causes
2. Review the information under the different sections.
3. Answer the questions below.
Questions
4. [3 marks] Use the website provided to name 3 roles of electrolytes in the body.
1st role Balance fluids in your body.
2nd role Maintain your blood’s proper pH level.
3rd role Carry electrical signals to power your nerves and muscles.
5. [1 mark] Which of the following ions are stated as ingredients in Pedialyte?
a. magnesium, calcium, sodium
b. chloride, potassium, sodium
c. calcium, potassium, nitrogen
d. chloride, potassium, salicylic acid
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6. [1 mark] When is drinking water alone not a sufficient remedy for dehydration?
Drinking water alone is not a sufficient remedy for dehydration because it does not have enough
electrolytes. Depending on how dehydrated you are you might need water and electrolytes.
Osteoporosis: One way in which osteoporosis develops in bones is by the accumulation of toxic metals in
bone tissue. In healthy human bones, zinc helps with bone strength and enzyme activity. Cadmium is a toxic
metal. Cadmium is found in certain foods that were grown in soils containing high levels of the heavy metal and
in cigarette smoke. Once in the body, cadmium competes with zinc to replace zinc in human bones. When
cadmium replaces zinc in bones, it weakens bones and can lead to osteoporosis.
Using the periodic trends you determined in this lab, explain why cadmium can compete with zinc. Use the
additional bullet points provided below about ionization energy and reactivity to help you answer the
question.
Moving down a group on the periodic table:
ionization energy decreases
reactivity increases
7. [1 mark] Locate zinc and cadmium on the periodic table. What do you notice about the location of these
elements?
Zinc and cadmium are in the same group but zinc is in period 4 while cadmium is in period
5.
8. [1 mark] Based on the reactivity trends summarized above, which element is more reactive: zinc or
cadmium? How do you know?
Cadmium is more reactive than zinc because of it’s location on the periodic table. The
further down a group means the more reactive an element is.
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