This video lecture from Periodic Classification of Elements and Periodicity (F.Sc. second year Chemistry) covers:Peculiar nature of hydrogen atom. Relation ship of the physical and chemical properties of alkali metals and the differences from hydrogen. Fors and againsts of putting hydrogen above halogens (Group 7A) and group 4A elements. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.