Question

What is the periodic trend I the variation of valency while going from left to right within a period explain your answer with reference to mordern table period 2 &3

Answer 1

Valence numbers do not vary as you go down a group, since the periodic table is arranged by atomic number and chemical properties. All members of a group have the same number of valence electrons. Group I has 1, Group II has 2, Group III - XII has 2, since only s or p electrons are counted as valence electrons, Group XIII has 3, Group XIV has 4, Group XV has 5, Group XVI has 6, Group XVII has 7 and Group XVIII (noble gases) have 8.

Answer 2

First the valency decreases then increases .....!!
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