Question

how to find chemical valency​

Answer 1

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If the number of electrons in the outer shell is between one to four, the compound is said to have positive valency. For compounds with electrons four, five, six, or seven, the valency is determined by subtracting the electron from eight. All noble gases except for Helium have eight electrons.

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Answer 2

Answer:

You need to know the atomic number. In first shell there will be 2 electrons and then 8 > 18 > 32. For example, we have calcium which has atomic no. 20. If you see electron distribution it will be

First shell > 20 - 2 = 18

Second shell > 18 - 8 = 10

Last shell can have only 8 electrons.So,

Third shell > 10 - 8 = 2

fourth shell > 2 - 2 =0

No. of electrons in last shell is the valency. So, valency of calcium is 2