Question

Can anyone explain me how to solve the valency of first 20 elements.

Answer 1

1st she'll has capacity of 2 electrons 2nd and 3rd shells have  capacity of 8 electrons and then 4th she'll has capacity of 18 electrons. According to their atomic number arrange electrons in shell 1 then 2 and so on. Example- oxygen atomic number is 8  that means it will fill 1st shell having capacity of 2 electrons. Then remained electrons will move to next she'll containing 8 electrons since 2 electrons are already in first shell remains electrons will fill 2nd shell to 6. Number of space left in last shell is valence of that element  

Answer 2

Hiii friend

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The valency of an atom is equal to the number of electrons in the outer shell if that number is four or less. Otherwise, the valency is equal to eight minus the number of electrons in the outer shell. Once you know the number of electrons, you can easily calculate the valency.
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Valency is the combining power of an element. Elements in the same group of the periodic table have the same valency. The valency of an element is related to how many electrons are in the outer shell.
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1st she'll has capacity of 2 electrons 2nd and 3rd shells have capacity of 8 electrons and then 4th she'll has capacity of 18 electrons. According to their atomic number arrange electrons in shell 1 then 2 and so on. Example- oxygen atomic number is 8 that means it will fill 1st shell having capacity of 2 electrons. Then remained electrons will move to next she'll containing 8 electrons since 2 electrons are already in first shell remains electrons will fill 2nd shell to 6. Number of space left in last shell is valence of that element
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