E - 32
GROUP PROPERTIES
NGSS: HS: PS1-1 Use the periodic table as a model to predict the relative properties of elements based on the
patterns of electrons in the outermost energy level of atoms. CC Patterns. SEP Planning and Carrying Out
Investigations. SEP Obtaining, Evaluating, and Communicating Information. SEP Analyzing and Interpreting
Data. SEP Engaging in Argument from Evidence. SEP Developing and Using Models.
In E-30 “Atomic Structure II”, you learned that atoms of elements in a group or family (i.e. vertical column) on the
Periodic Table all have the same number of electrons in their outermost main energy level (i.e. valence electrons). For
those elements that are in the Main Group (i.e. Groups 1-VIIIA), these valence electrons are in the s (and possibly p)
sublevel(s). You learned that losing or gaining these valence electrons, in order to take on the electron configuration of
the closest Noble Gas to the given element, makes that element more stable (i.e. the Octet Rule). In so doing, the
element has become an ion. Thus, members of a group or family all have the same oxidation number when they
become ions. It should also be noted that, since ions are more stable than atoms for all elements except the Noble
Gases, atoms “compete” to form ions. Therefore, a stronger (more reactive) element will replace a weaker (less
reactive) element in a compound as a result of “winning” the electron competition and becoming an ion. Also, there
are seven elements that increase their stability by becoming molecules consisting of two covalently bonded
atoms. The seven diatomic elements are H2, N2, O2, F2, Cl2, Br2, and I2 (Note: They make a “seven” shape on the
Periodic Table.).
What else do the members of a group have in common besides valence electrons and oxidation numbers? Do the
members of a group behave similarly in chemical reactions? What is the trend in reactivity as we go down or up a given
group? In this lab, you will make qualitative observations about the reactivity trends of the Group IA (Group 1):
Alkali Metals and the Group VIIA (Group 17): Halogens. From this, you will use inductive reasoning to derive the
reactivity trends for all Main Group metals and non metals.
________________________________________________________________________________________________
Purpose:
1. To conclude the periodic trend for the reactivity of the Group IA (1): Alkali Metals using evidence from the E32 lab.
2. To conclude the periodic trend for the reactivity of the Group VIIA (17): Halogens using evidence from the E32 lab.
3. To explain what happens when a stronger (more reactive) elemental metal encounters a weaker (less reactive)
metal in an ionic compound (or a stronger elemental non-metal and a weaker elemental non-metal in an ionic
compound).
4. To list the chemical symbols of the seven diatomic atoms.
5. To list two possible sources of error in the E-32 lab and explain how they would affect the results of the lab.
Materials:
Day I glass reaction plates
forceps
phenolphthalein dropper bottle
lithium (Li) jar
sodium (Na) jar
potassium (K) jar
Day II small test tubes
parafilm
bromine water (Br2) dropper bottle
organic solvent dropper bottle
potassium bromide (KBr) dropper bottle
test tube rack
chlorine water (Cl2) dropper bottle
iodine water (I2) dropper bottle
potassium chloride (KCl) dropper bottle
potassium iodide (KI) dropper bottle
Safety Alerts: Goggles, long pants, aprons, closed toed shoes / vapors, eye and skin irritants, stains, glass.
Special Notes:
The alkali metals are very reactive with moisture! Use with caution and DO NOT leave lids open or allow
moisture to get inside jars! DO NOT put wet forceps into jars! Close lids immediately after obtaining a single
piece of metal! If the kerosene or mineral oil storage liquid is low in your jars, let your teacher know
immediately!
Molecular halogens are toxic and should not be inhaled! Use halogens in a well ventilated area! Some people may
experience eye or skin irritation after exposure to halogens. If this happens to you, let your teacher know
immediately! Also, if you have a known allergy to chlorine or iodine, let your teacher know before proceeding
with this lab!
Procedure:
Note: This may be done as a demonstration by your teacher.
Day 1 - the Reaction between Alkali Metals and Water (i.e. HOH)
1. Obtain three glass reaction plates and one forceps. Make sure they are clean and dry. Set them at your workstation.
2. Put approximately 25 mL of distilled water in each reaction plate. Add three drops of phenolphthalein to each
reaction plate.
3. Making sure you are wearing your goggles, carefully open the lithium (Li) jar and remove one piece of lithium with
your clean, dry forceps. Close the lid immediately.
4. Drop your piece of lithium (Li) into your first glass reaction plate. Record your observations in your data table. Be
sure to note the color of the water!
5. Repeat steps 3 and 4 with sodium (Na). Make sure to record your results in your data table. Make sure to note which
reaction was more vigorous, Li + HOH or Na + HOH.
6. Repeat steps 3 and 4 with potassium (K). Make sure to record your results in your data table. Make sure to note
which reaction was more vigorous, Li + HOH, Na + HOH, or K + HOH.
7. Make sure to clean up your workspace and put all materials away.
8. Use your black textbook to look up what phenolphthalein indicates at its various colors. Record your findings in
your data table.
Day 2 - the Reaction between Free Halogens and Halide Ions
Note: This may be done as a demonstration by your teacher.
Control Group
1. Obtain a test tube rack and 12 small test tubes. Make sure the test tubes are clean and as dry as possible. Set them at
your workstation.
2. To one test tube, add 15 drops of chlorine water (Cl2) and 15 drops of organic solvent from the appropriate dropper
bottles. Place a small piece of parafilm over the test tube and shake to mix. Record the color in the organic solvent
layer in your data table.
3. To a second test tube, repeat step 2 with bromine water (Br2) and organic solvent. Record the color in the organic
solvent layer in your data table.
4. To a third test tube, repeat step 2 iodine water (I2) and organic solvent. Record the color in the organic solvent layer
in your data table.
5. Set these three test tubes aside in one area of your test tube rack for later reference.
Experimental Group
6. To one test tube, add 15 drops of chlorine water (Cl 2), 15 drops of organic solvent, and 15 drops of potassium
chloride (KCl) from the appropriate dropper bottles. Place a small piece of parafilm over the test tube and shake to mix.
Record the color in the organic solvent layer (i.e. the “oily bubble layer”) in your data table.
7. Repeat step 6 with each of the following combinations:
Cl2 , organic solvent, and KBr Cl2 , organic solvent, and KI
Br2 , organic solvent, and KCl Br2 , organic solvent, and KBr Br2 , organic solvent, and KI
I2 , organic solvent, and KCl
I2 , organic solvent, and KBr
I2 , organic solvent, and KI
Make sure to record the color in the organic solvent layer for each test tube in your data table. Be careful to keep track
of which test tube is which!!!
8. Use soap and water to clean out your test tubes. Then, make sure to clean up your workspace and put all materials
away.
Data Table:
DAY ONE:
Observations
Solution color
Degree of reactivity (i.e. high, medium, or
low)
Li + HOH
Na + HOH
K + HOH
Phenolphthalein indicates an _____________________ when _________________ in color and a
____________________ when ___________________ in color.
DAY TWO:
CONTROL GROUP
Color of organic
layer
Cl2
Br2
I2
EXPERIMENTAL TRIALS
KCl
(Color of organic layer)
KBr
(Color of organic layer)
KI
(Color of organic layer)
Cl2
Br2
I2
** Place a star in the boxes in which the color of the solution has changed from the original color (refer to the
control group).
Analysis:
for Day 1 - the Reaction between Alkali Metals and Water (HOH)
1. Write balanced equations for the three reactions for Day 1. To do this, first, use your knowledge of the purpose
of phenolphthalein to determine the first product. The second product is a gas. Once you have the two products
for each of the three reactions written with correct subscripts, balance the equation with coefficients.
2. Write a reactivity series for the three alkali metals you used using a greater than symbol between each metal
_____  _____  _____ . (Hint: Which metal gave the biggest spark in water?).
for Day 2 - the Reaction between Free Halogens and Halide Ions
3. Write equations for the nine reactions for Day 2. For the three reactions that actually worked, write the correct
products (Hint: One will be an element and one will be a compound.) and then balance those equations with
coefficients. For the six reactions that DID NOT work, recopy the reactant side of the equation followed by the
letters NR (i.e. no reaction).
4. Write a reactivity series for the three halogens you used using a greater than symbol between each non-metal
_____  _____  _____ . (Hint: You must first decide which three of the nine reactions worked. To do this,
compare the expected color (See your control group data!) in the organic layer to the actual color (See your
experimental group data!). If they are NOT the same, it reacted. For example, if Cl2 was added to the first
reaction, what color should be in the organic layer? Was it? Was there a reaction? Then, rank the three halogens
by remembering that a stronger element will replace a weaker element in a compound.).
Questions:
1. Because the Alkali Metals react with moisture, how must they be stored?
2. Fill in the blanks: Phenolphthalein indicates a(n) __________ when __________ in color and a __________ when
__________ in color.
3. In the reactions between the Alkali Metals and water, which product did phenolphthalein help you to discover. How
(Hint: Look up the Arrhenhius definition of a base.)?
4. Given the elements present in the reactions between the Alkali Metals and water, what possible gases could be given
off? What test could be used to confirm the correct gas’ identity? What tests could be done to eliminate other gases
(Hint: How could you make use of an inverted beaker and a wood splint?)?
5. When an Alkali Metal becomes an ion, does it gain or lose an electron?
6. Of the Alkali metals you used, which was the strongest (most reactive)? the weakest (least reactive)?
7. Given the reaction, F2 + KCl, will a reaction occur? If so, write a balanced equation for it.
8. Which two Alkali Metals are vital minerals for human nutrition (Hint: Use a Biology book and look under
minerals.)?
9. What color are the three Halogens you studied in water?
10. Where was the organic layer compared to the water layer in the reactions of the Halogens with the Halides? Why
(Hint: What do we know about objects that float/sink in water?)?
11. When a Halogen (non-metal) becomes an ion, does it gain or lose an electron?
12. Of the Halogens you used, which was the strongest (most reactive)? the weakest (least reactive)?
13. Which three Halogens are vital minerals for human nutrition (Hint: Use a Biology book and look under minerals.)?
14. Fill in the blanks: A __________ element will replace a __________ element in a compound.
15. Name the seven diatomic elements.
Conclusion:
Mind Prober:
1. Using the Alkali Metals and the Halogens (non-metals) as a guide, where would you expect to find the strongest
(most reactive) Main Group metals? Non-metals?
2. Predict what would happen in each of the following reactions:
a. Ba + MgCl2 
b. Ca + SrCl2 
c. Na2S + O2 
d. Na2Se +S 