IONIC SPEED DATING – Instructor Information
This activity is used as a reinforcement activity following my use of JCE Classroom Activity #113: An Interlocking
Building Block Activity in Writing Formulas of Ionic Compounds.
Ruddick, Kristie R and Parrill, Abby L, An Interlocking Building Block Activity in Writing Formulas of Ionic
Compounds, Journal of Chemical Education 2012, 89 (11), pp 1436-1438.
Materials: Blue building blocks to represent cations & Red building blocks to represent anions.
For one set each of A – D as described in the table below, you will need
Blue: three 3 x 1, nine 2 x 1, nine 1 x 1
Red: six 3 x 1, eight 2 x 1, nine 1 x 1
The knobs on each block represent the valency or charge of the related ion. For example, a 1 x 3 blue block can
represent an aluminum ion with a charge of 3+ and a 1 x 1 red block can represent a chloride ion with a charge of
1-. Therefore, you will need 3 red (chloride ion) blocks to neutralize the blue (aluminum ion) block. The neutral
formula units are rectangular and are made up of the lowest whole number ratio of blocks. (All blue blocks must be
in a single row and all red blocks must be in a single row.)
I make up a variety of sets of blocks and keep them in baggies labeled Set A, Set B, Set C and Set D. Students will
rotate through the sets with only 2 minutes per set. (Create as many sets as you like. Sets A – D are described
below.) I created 6 baggies of each set and have students rotate through sets A – B. Remind students to write the
formulas and names of the compounds as they manipulate the sets. They will not have time to complete that part
later. (I do allow for a minute between sets to allow students to complete the formula and name of the last
compound they built.) Students should disassemble the formula units before they move to the next set. They may
use ions more than once in each set, but they must be able to build a complete formula unit in order to include it
in the data table (ie. Ca2N3 cannot be made from set A because there is only one N 3- available).
Use permanent marker to write the ion names on the appropriate red or blue blocks. Remind students that there
must be a blue line of blocks and a red line of blocks for each formula unit.
Set
A
Blue (cations)
3 Na+, 2 Ca2+
Red (anions)
2 P3-, 3 Cl-, 1 N3-
B
2 Ca2+, 2 Al3+, 2 K+
3 S2-, 2 Br-
C
3 Ba2+, 1 Ca2+, 2 Li1+
3 S2-, 2 F1-, 1 N3-
D
2 Ag+, 1 Al3+, 1 Ba2+
2 O2-, 2 I1-, 2 P3-
Possible compounds
Na3P, NaCl, CaCl2, Ca3P2,
Na3N
CaBr2, Al2S3, CaBr2, K2S,
KBr, CaS
BaS, BaF2, CaF2, CaS, Li2S,
LiF
Ag2O, AgI, AlP, BaO, BaI2
The number of compounds found per set may vary per group because of the time restraint. The teacher may
prefer to ignore the time involved and require students to complete only one set or a combination of sets.
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