a. How does valency vary in a group on going from top to bottom?
b. How does the number of valence electrons vary in a period on going from left to right and from top to bottom in a group?
(a) Valency remains same on moving from top to bottom in a particular group. This is because the outermost electronic configuration of all the elements in a group remains same.
(b) On moving from left to right in a period, the number of valence electrons in elements increases from 1 to 8. The elements in a period have consecutive atomic numbers.
On moving down a group in the periodic table, the number of valence electrons in the elements remains the same.
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