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How to find an Element's valency (Technique 1) - The Sindhupalchowk Diary

Note: This is just a technique to calculate and doesn’t explain ‘WHAT is valency and WHY is it so’. I have tried the technique with just first 20 elements, which are the must necessary ones according to our curriculum in Nepal. Please check the technique with more elements and let me know if it doesn’t work.
Background :
Valency is one important concept in chemistry. Being able to calculate it helps students with other chapters in chemistry like writing molecular formula, chemical reactions etc. So, I have been trying hard to make each student calculate valency.
During my C2SATs class of grade 7 taken by grade 9 students, one of the student Gokul Lamichhane was using a different technique to teach calculation of valency. I asked him where he learnt it. He got it from an engineer relative. I found it amazing. It was as easy as counting chickens. However, he didn’t know how to give sign to the valency.
Later, I dug into the technique. It was nothing new. It was always there. Elements repeat their properties after each 8th group. I found the technique to give signs as well. So, I am explaining the technique here.


Things to know

1. First, the students need to remember this table. This isn’t rocket science. It’s a very easy table to remember.


Figure 1: Table 1
Note:  NA = Sign Not applicable.
2.   Elements in serial order.

STEPS

  1.      Find the atomic number of the element whose valency is to be calculated. This is equal to the serial number of the element. Example: Sodium lies in 11th number, so it’s atomic number is 11.
  2.   In the table, count consecutively from left to right for number equal to atomic number of the element.
    Example: For Sodium, count from 1 to 11.
  3.  Once you have finished counting, you reach a particular cell (box) in the table. The number in the box is your valency and the adjacent sign is your sign.Example: For Sodium, I reach 3rd box which has 1 in it. So, 1 is the valency. The adjacent sign is +. So, the valency of Sodium is +1.


FINAL NOTE:

This technique is not applicable for the sign of Hydrogen. Hydrogen has some attitude problem, I guess. ;)

- I recommend teachers and teachers to try this technique to see if it really works. If it fails at some point, please let me know.
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