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Question
How does number of (i) valence electrons (ii) valency; vary on moving from left to right in the second period of a periodic table?
Solution
The valence electrons in the same shell (outermost shell) increase progressively by one across the period. The first element hydrogen has one valence electron and helium has two valence electrons.
On moving from left to right in a period, valency increases from 1 to 4, then falls to one and ultimately to zero in the last group.
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