Question

What is the periodic trend in the variation of valency while going down agrpup ? Explain with reference to group 1, group 2 and group 18.

Answer 1

valency doesn't change while going down a Group due to the same number of Valence electrons.group 1 elements have valency 1
group 2 elements have the valency 2 and group 18 elements have their valency 0 due to their inertness.
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Answer 2

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.