Aim: To teach the periodic table and highlight some of the Significant concept(s). The concepts we want the students to retain for years into the future are:

1. Understand that there is a systematic way to study the properties of all the elements known to us.
2.  The Periodic table gives us a way predict the behaviour of any atom in the material world.

Use the Thinking task framework to understand how the periodic table is arranged i.e. the first significant concept listed above.

At the end of each exercise, there would be one more parameter added to the list of strategies,

leading up to being able to place any element in the periodic table by being aware of the logic applied in its design. There would be a series of lessons, each one focused on a single parameter.

The algorithm built by them would eventually be a list of parameters or precise characteristics that could be used to accurately place any element in the periodic table.

As a preparation to these lessons, the teacher should prepare

1. Lots of blank cards (to be filled in as the lesson progresses.....could be a different colour for each parameter....the values could be added by the students with markers as they go on...etc.)

2. A BIG blank periodic table for each student or each group of students as the case may be.

To get an idea of how the teacher might progress through the lesson, please take a look at the link:

Step 1. There are 20 cards. On each one is the name of an element and its atomic number. Write the valence electrons for each and then place them on the blank periodic table. Now look at the pattern.

Step 2. elements with the same valence electrons occupy the same vertical column, called groups. At this stage the students can then add this parameter, "valence electrons" to their algorithm, which is a list of such parameters and the values that may be changed to locate them in the table

The table here provides a frame of parameters and values that could be used to build an algorithm:

 Parameter Value Patterns/observations Comment Additional comment Atomic number 1, 2.…till 20. Each value in this parameter yields one specific element in the periodic table The elements are organized in order of  increasing atomic number State Solid, liquid or gas: The 3 values yield another picture 1. All the gases  end up on the right hand side of the periodic table, together. 2. There are very few elements that are liquid at room temperature3. Most elements are solids at room temperature. That so few elements are liquid at room temperature could be the starting point of a dedicated set of investigations. Metal/ non metal 2 values to begin with Non metals come on right hand side of the table and the metals come on the left hand side Interestingly there are a few elements that DO NOT find a place in the periodic table using this parameter and the 2 values originally devised On a small scale, here is an opportunity to illustrate to the students that the algorithm they had been working with fails…..so there is a need to go through step 3 which is about reflection and improving the algorithm of step 2. After step 3, the students add one more parameter to their list to cover these elements Metalloids/non metalloids 2 values Metalloids emerge as a group arranged in a zig zag, step like fashion, cleaving the periodic table into two parts (even if the edges are jagged, it is still a boundary) At this point, in the traditional style of teaching, also there would have been a need to introduce a new term here. However the thinking task framework would work in a slightly different manner. Must go back and change the algorithm. The new term is metalloid (given by the teacher) and the other value assigned to this parameter is simply non-metalloid. Simple! Number of valence electrons 1, 2, 3, 4,5, 6, 7 and 8 The 8 values thus chosen would yield 8 groups in the periodic table Out of these,  4 groups are then assigned 4 group names (The teacher facilitates; the students can also look at standard periodic table formats on the internet where these group names are used) An opportunity exists here to introduce/reinforce the idea of “variables” as used in science.

Step 3. As a part of looking at the effectiveness of the algorithm they have created, some activities that allow them to use those few parameters that they have been working with, in a new situation would be a way to test their algorithm. And after they are confident with these, introduce a task where these parameters would not work. This is going back to step 1. Introduce an aspect in the task where the built algorithm fails.

Its possible to extend this, using the same ENV model, using some more parameters like melting point, ionization energy, electron affinity …etc. maybe for the next age group.
After working with this  ENV model, there are several activities that the students could do to test the algorithm they have created.

Activity:

1. There is an empty periodic table (empty cells; format the same as the modern periodic table)

2. There are cards with different values of the parameters the students have been working with above. The cards do not carry the name of the element but are numbered A, B, C…etc.

3. The students use the ENV model they developed above to paste these cards in the periodic table.

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