Purpose
To observe and explain how the chemical properties of Halogen ions (often called halide ions) are based upon the arrangement of
electrons in atoms
Background
Ionic compounds are formed when metal cations transfer one or more valence electrons to non – metal anions. This makes sense
when you recall that metals are relatively large atoms with low ionization energies, while non – metals are smaller atoms with
relatively high ionization energy and electronegativity values. Ionic compounds share many common characteristics such as high
melting points. Ionic compounds will dissolve into their component ions when placed in water, allowing them to conduct
electricity. They are therefore called electrolytes. When ionic compounds dissolved in water as solutions are mixed, they will
often react and produce crystalline solids that fall out of solution. A precipitate is a solid that is formed when a combination of 2
or more liquid solutions are combined. In this lab investigation you will see precipitates formed as a result of mixing ionic
compounds. Pb 2+
Materials
Pencil
Paper
Ruler
Well Plate
Silver Nitrate Ag NO3
Lead (II) Nitrate Pb(NO3)2
Potassium Fluoride KF
Potassium Chloride KCl
Potassium Bromide KBr
Potassium Iodide KI
Procedure
1.
2.
3.
4.
Using the guide below, place the correct chemicals in the correct wells on your well plate. Only ONE chemical may be in
your possession at a time. You should end up with 2 chemicals in each well, allowing you to observe any reaction that
may take place.
Add 3 drops of each chemical into the correct location. Be sure that when you add the second chemical it mixes with the
first chemical. Be careful and DO NOT touch the dropper into the chemicals that are already in the well.
Wait for 10 seconds, and then observe the appearance of the mixture in each well. Record your observations in data
table #1.
CLEAN UP: Wash and dry the well plate thoroughly. Clean your lab station thoroughly and wash your hands when
you are finished.
Data Table #1
Ag NO3
Pb(NO3)2
KF
Formula: (combine Ag 1+ and F 1-)
Formula: (combine Pb 2+ and F 1-)
Well Plate #1 – Observations:
Well Plate #5 – Observations:
KCl
Formula: (combine Ag 1+ and Cl 1-)
Formula: (combine Pb 2+ and Cl 1-)
Well Plate #2 – Observations:
Well Plate #6 – Observations:
KBr
Formula: (combine Ag 1+ and Br 1-)
Formula: (combine Pb 2+ and Br 1-)
Well Plate #3 – Observations:
Well Plate #7 – Observations:
KI
Formula: (combine Ag 1+ and I 1-)
Formula: (combine Pb 2+ and I 1-)
Well Plate #4 – Observations:
Well Plate #8 – Observations:
Analysis Questions
1.
2.
3.
4.
5.
6.
7.
Complete the chemical formulas in data table #1.
List all of the halogens. In which group on the periodic table are the halogens located?
Write the electron configuration for each of the halide ions.
What do all of the electron configurations of all of the halide ions have in common?
What are the characteristics and uses of the Halogens? (Use R34 – R35 in the orange text book)
What will the ratio in the chemical formula always be when a halogen and an alkali metal form an ionic compound?
Why? (Hint: Think about why we use criss – cross method.)
What will the ratio in the chemical formula always be when a halogen and an alkaline earth metal form an ionic
compound? Why?