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  Code: TLM- Sc- 001 Age: 10-13 yrs   Name: Valency Cards (Chemistry)

Each set contains   
Jigsaw shaped pieces representing positive and negative valencies. The pieces are colour coded (positives are yellow and negatives are red). The ions also have the names written in English, Gujarati & Hindi. For e.g.

How to use
This material can be used by a single student or two students. It helps them visualise the concept of Valency. The Chemical Formulae of common chemical compounds can also be determined by using the material as described below.

Step 1: Group of 2 children is formed. The Valency Cards are given to them..

Step 2: Each student takes a fresh sheet of paper, draws a margin, writes her name and date on the top right hand corner and name of the exercise in the center of the page.

Step 3: Then they create a table as shown below.
No Name of compound Formula
1.

2.

3.

etc.

    
The educator reads out the names of the chemical compounds to them. Each student determines the Chemical Formula using this material.

Step 4: The educator need not give the compounds described below which are only for illustration. She can choose any 10 compounds as long as they fit into this material.
1 Sodium Chloride 7 Lead Sulphate 13 Aluminium Phosphate
2 Ammonium Chloride 8 Hydrogen Sulphide 14 Potassium Borate
3 Silver Bromide 9 Potassium Iodide 15 Calcium Phosphate
4 Ferrous Sulphate 10 Hydrochloric Acid 16 Lead Oxide
5 Calcium Sulphite 11 Lead Sulphate  
6 Ferric Chloride 12 Copper Hydroxide  
     
Step 5: For determining the Chemical Formula all the pieces are arranged - Yellows (positive ions) on the left and Reds (negative ions) on the right as shown below:


Step 6: 1. To find the chemical formula the players join the jigsaw pieces of the respective ions. For e.g. the educator says "Sodium Chloride"; the players write -

Sodium Chloride

2. The player picks up the root ion card - Sodium or Na+ and places it as below:

3. Then the player picks up the other ion card, Chloride or Cl- and places it against the root ion

Na++ Cl- = NaCl
Sodium Chloride Sodium Chloride

Then the player counts the number of pieces of each ion i.e. 1 Na (Sodium) and 1 Cl (Chloride) gives the formula NaCl

Yet another example:

1. The educator says Calcium Chloride. The players write -
Calcium Chloride
2. The players then pick up the root ion card - Calcium or Ca++ and place it as below:

3. Then the players pick up the other ion card, Chloride or Cl- and place it against the root ion. Immediately the players realise that the picture is incomplete and that one more piece is required to complete the picture.

Then the players counts the number of pieces of each ion i.e. 1 Ca (Calcium) and 2 Cl (Chloride) gives the compound CaCl2.

Step 7: To check, the educator sees the formula and also the various pieces fitted together to confirm answers.

Development aspects:

1. Valency is one of the most fundamental concepts in chemical bonding, chemical reactions, etc. This game is used to help children learn the concept of valency and its application in Chemistry.

All atoms have electrons and protons. Electrons are arranged in concentric orbitals around the nucleus. Orbitals can accommodate 2 electrons in the first, 8 in the next 2, then 18 in the next 2 and so on. Electrons in the outer orbitals are loosely bound to the nucleus due to the distance. All atoms try to attain the stable octet state (8 electrons in the outermost orbital). For this they either lose or gain electrons whichever is easier.

Valency is the minimum number of electrons that any atom loses/gains to reach a stable state (octet state). Valency thus determines how active or passive an ion is. Ions which can easily lose or gain an electron to reach a stable state are highly reactive.

2.The game may also be extended to helping children understand and remember significant chemical and physical properties of various ions. These properties may be printed on the reverse of the cards and then these cards can be used as flash cards.

3.Children can learn to balance simple chemicals equations with the help of this game. For e.g. the simple equation

a) CuSO4 + Mg MgSO4 + Cu

b) ZnSO4 + MgCl2 MgSO4 + MgCl2

Mg displaces Zn in Zinc Sulphate Solution

4. There is also an element of cognition in this game as children develop a mental picture of the various ions and given two ions they immediately tell the formula without having to play the game. They are now able to play the game in their mind.

Teaching Learning Materials (TLM) can make learning much more effective and fun in classrooms.

Taleem is an initiative in this direction.

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