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Standard VIII

Chemistry

Introduction to Hydrogen

sodium and al...

Question

sodium and aluminium have atomic numbers 11 and 13 respectively.they are separated by 1 element in the periodic table,and have valencies of 1 and 3 respectively. chlorine and potassium are also separated bt 1 element in the periodic table( their atomic nos. being 17 and 19 respc.) and yet both have the valency of 1.Explain the difference.

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Solution

Valency of an element depends on the number of valence electrons in the element.Valency = number of valence electrons if the number of valence electrons is 1-3 and 8- number of valence electrons if the number of valence electrons is 4-8.
Sodium has 1 valence electron.So, it valency is 1.
Aluminium has 3 valence electrons.So, its valency is 3.
Potassium has 1 valence electron.So , its valency is 1.
Chlorine has 7 valence electrons.Its valency is 8-7 =1.

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