Name: _________________________________________________________ date: __________ hr: ____________
2016-2017
CHEMISTRY LAB- Periodic Trends- CH 05
Introduction:
The structure of the periodic table is such that elements with similar properties are aligned vertically in columns called
“groups or families”. This leads to smoothly varying trends in properties such as ionization energy, electronegativity, and
atomic radii as one moves both down a specific group and horizontally along a given period.
The reactivity of the elements also follows well-defined trends both within groups and across periods. In this miniexperiment, you will explore a few trends in reactivity.
Elements in the periodic table are organized by increasing atomic number. As atomic numbers increase, so does the
number the electrons. Electrons, and specifically valence electrons, are important in determining how an atom interacts with
other atoms. The elements in a group have similar properties because they have the same number of valence electrons, which
are found in similar electron configurations.
Part 1: Trends in the Properties within Groups
Watch the video on the “Alkali Metals in Water, Accurate!”(2:21 min) http://www.youtube.com/watch?v=uixxJtJPVXk
1.
Name all the elements that are Alkali Metals:__________________________________________________________________
2.
How many valence electrons do the Alkali metals have?_________________________________________________________
3.
State the trend in reactivity for the alkali metals as you go down the group._________________________________________
4.
What energy level are the valence electrons found on in the element Lithium?______________________________________
5.
What energy level are the valence electrons found on in Potassium?_______________________________________________
6.
What energy level are the valence electrons found on in Cesium?_________________________________________________
7.
Using the information from #4-#6, EXPLAIN the group trend in reactivity of the Alkali Metals.
________________________________________________________________________________________________________
Group II, Alkaline Earth Metals (4:57 min) https://www.youtube.com/watch?v=T7K4Qi5PiFg
1.
Which elements are considered to be Alkaline Earth Metals? ____________________________________________________
2.
How many valence electrons do these elements have?__________________________________________________________
3.
Name 2 physical properties of these elements ________________________________________________________________
4.
Name 1 chemical property of these elements._________________________________________________________________
5.
What do they mean when they say these elements are very “electro-positive”?_____________________________________
6.
How do they compare to the Alkali Metals in hardness, strength, and density?_____________________________________
7.
Access this website and explain the general period and group trend for reactivity in metals and non-metals:
http://edtech2.boisestate.edu/lindabennett1/502/periodic%20table%20e%20config/PTable_trends%20aroun
d%20table.html
Part 2: Complete the chart below, then continue on to the procedure portion of the lab.
Metals
Long hand electron
configuration for the neutral
atom of the element
Lewis Dot
diagram
Write the
symbol of
the ion.
Long-hand electron
configuration for the ION of the
element
What element
is it
isoelectronic
to?
Mg
Al
Cu
Zn
Part 3 (day 1)
Materials
Goggles
Electronic balance
10 mL graduated cylinder
Triangular file
two 50-150 mL beakers
forceps
plastic pipette
paper towel
one post and one pre 1982 penny
1.0 M Hydrochloric Acid
weighing paper
1.
Copper and Zinc are both key components in the composition of pennies made after 1982. Pennies that were made before
1982 are composed primarily of copper. Pennies made after 1982 are composed primarily of Zinc.
2.
Obtain two 50 mL, 100 mL, or 150 mL beakers. Place your name and your partners name on each beaker using a pencil. If
you need a sticky label to write you name on let your instructor know. Label on beaker PRE and the other POST.
3.
Obtain two pennies; one pre 1982 and one post 1982.
4.
Record two physical properties of each penny in the table below.
5.
Doing this step over a paper towel: file a notch in four sides of each penny.
6.
Mass out each penny and record the mass in the table below.
7.
Place each penny in the proper beaker.
8.
Using a plastic pipette and graduated cylinder place 10.0 mL of hydrochloric acid into each beaker.
9.
Place the beakers on the tray in the chemical hood to be saved overnight.
Pennies
Observations- before
placing in HCL
Mass before
placing in
HCl(g)
Mass after
placing in HCl
(g)
Observations after placing in
Hydrochloric Acid-immediate
and over night
Pre 1982
Post 1982
10. What sign of a chemical change did you witness when you placed the pennies in each beaker of HCl? Which penny
produced the larger reaction? (you may need to wait 2-3 minutes)
Part 4 (Day 2)
Materials
Goggles
Electronic balance
weighing paper
one 50-150 mL beaker
forceps
paper towel
11. Using a pair of forceps, place each penny in a beaker of tap water to rinse them off. Now, place each penny on a piece of
paper towel. With a different paper towel pat dry each penny (be sure to wash your hands!)
12. Make 1-2 observations for each penny and record in the table found in Part 3.
13. Using a piece of weighing paper mass out each penny and record in the data table found in Part 3.
12. After seeing these results, is copper or zinc more reactive with Hydrochloric Acid? __________________________________
13. Page 161: Define electronegativity:
14. Hydrochloric Acid is a molecule consisting of Hydrogen and Chlorine. Which element is the most electronegative?(pg 161)
15. Draw Lewis dot diagram for Hydrogen. __________________Draw Lewis dot diagram for Chlorine. ________________
Part 5
Materials:
Goggles
Four medium sized test tubes
Test tube rack
1.
2.
3.
4.
5.
Metals: Mg, Al, Cu, Zn
1.0M Hydrochloric Acid
Plastic pipette
Forceps
Sand paper
Obtain, all materials except the hydrochloric acid. Now obtain ONE piece of each metal in the data table below.
Record two physical properties of each metal and place in the first column of the chart.
Sand down each piece of metal, the best you are able. Do this over a piece of paper towel.
Place each metal in a large test tube separate from one another. NOW pick up the HCl.
Using a plastic pipette add just enough Hydrochloric Acid (HCl) to cover the piece of metal. Let sit for approximately 3-5
minutes then record your observations, be sure to feel the bottom each test tube.
Metals
Observations before
adding HCl
Immediate observations and after 3-5 minutes
in HCl
Rank from most to
least reactive in
HCl( 1 being least,
4 being most)
Mg
Al
Cu
Zn
8. Comparing the elements in period three, Aluminum and Magnesium. Which was most reactive with the HCl? WHY do
you think one was more reactive than the other? Explain.
9. Comparing the elements in period four, Copper and Zinc. Which was most reactive with the HCl?
10. Do your results in #9 correspond to your results in PART 3 of the experiment?
11. Circle the atom with the larger atomic radius: Magnesium/Aluminum
12. Circle the atom with the smaller atomic radius: Copper/Zinc
13. What is the effective nuclear charge felt on the last energy level of a Magnesium atom?
14. What is the effective nuclear charge felt on the last energy level of an Aluminum atom?
http://www.xtremepapers.com/revision/gcse/chemistry/metals.php Use this website to help answer the questions
below.
15. Reactivity of a metal is determined by what?
16. According to the “activity series” is copper or zinc more reactive?
17. Scroll down and look at the chart of data from the same reactions that you and your partner observed. Are your results the
same as the data listed on this chart?
18. How many valence electrons does Zinc have? How many valence electrons does Copper have? Where is Zinc on the
activity series verses copper?
19. Search the internet…………….. please include the website you use! If Zinc has more valence electrons than Copper, then
why is Zinc more reactive than copper in hydrochloric acid?