Coordination Compounds: Independent Study

The purpose of this unit is to acquaint you, the student, with some research techniques and to involve you in the discovery learning process. You will be given a topic to work on and some guidelines for what you should accomplish. You will work in groups of three and share your results with the other members of your group.

The problem you will be studying is a classic example of research in chemistry, the structure of a coordination compound. This work led to the first Nobel Prize awarded to an inorganic chemist, Alfred Werner.

The following scientific facts about the compounds of cobalt listed below are well proven and accepted. The overall goal you have is to derive a structure for the three (four?) different compounds that agree with the data. In the process you will learn many new terms but you will also review many ideas and have to adapt them to the new subject matter.

Required Software (as of March 2020, the software has been freely available for an indefinite time because of COVID-19. A ChemEd X subscription may be required after the pandemic.): Werner/Joergensen Bond Theory  & Evolution of Bond Theory 

Three formulas are known for these compounds.

Formula Color of Compound
CoCl3·6NH3 yellow
CoCl3·5NH3 purple
CoCl3·4NH3 one green and one violet

In addition the following reaction regarding the compounds are known:

Reaction of Compounds
CoCl3·6NH3 + excess AgNO3 → 3 moles AgCl ppt
CoCl3·5NH3 + excess AgNO3 → 2 moles AgCl ppt
CoCl3·4NH3 + excess AgNO3 → 1 mole AgCl ppt (both colors do the same)
complex ions
coordination compounds

coordination compounds, complex ions

Procedure time: 
> 90 minutes
Prep time: 
20 minutes
Time required: 

5 class periods for entire independent study project


This student activity accompanies the article, A guided group inquiry lesson on coordination compounds and complex ions.


Schedule of events

Bring your book everyday for this chapter!

Day One:

Ponder the question and try to devise a structure. Show guess structures to the teacher. Try again.

Day Two:

Use the JCE: Software Programs on the Werner/Joergensen Controversy and on Bonding. Work through these with a partner. Try for another structure based on this information.

Day Three:

Define the following terms (or people) and look up pertinent information.

complex ion
coordination compound
ion counter
coordination sphere
molecular geometry
dative bond isomer
stereo isomer
geometric isomer
ionic bond
structural isomer
covalent bond
lewis base
Alfred Werner
Mads Jorgensen

Look up the rules for how to name coordination compounds and complex ions. Name the following compounds:

  1. K2[CoCl4]
  2. [Cu(NH3)4]SO4
  3. [FeCl4]
  4. K4[Fe(CN)6]
  5. K2[PtCl4

Write formulas for the following compounds:

  1. Tetrachloroferrate(II) ion
  2. Pentammineaquaruthenium(III) ion
  3. Potassiumamminetrichloroplatinate(II)
  4. Hexamminecobalt(III) chloride
  5. Triamminebromoplatinum(II) chloride

Day Four:

Laboratory Exercise on complex ion formation.

Day Five:

Discuss results and review for test


provide simulation

The author gratefully acknowledges the assistance of Daniel Rabinovich of UNCC with the graphics for this article. A Bonding Theory/ The Werner-Jorgensen Controversy, A Review of a two part simulation:

Michael A. Morgan Francisco Bravo Medical Magnet High School, Los Angeles, CA 90033


General Safety

For Laboratory Work: Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).  

For Demonstrations: Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.

Other Safety resources

RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies