Question

give scientific reason why elements with larger electro positivity or electro negativity is highly reactive

Answer 1

only electro positivity is highly reactive.
u r wrong.

Answer 2

The definition of electropositivity is the tendency of an atom to lose electrons from its outermost shell and become positively charged ion (cation). Now when we look at the periodic table, we see two groups that contain highly electropositive elements which are alkali metals (group I) and alkaline-earth metals (group II). However alkali metals are more electropositive since they need to lose only one electron to complete their octet (stable electronic configuration),

In a group, you have to consider 2 factors, atomic size and effective shielding. Down the group, the size of an atom increases because of increasing number of shells and observe that the outermost electron gets further away from nucleus as the number of shells increase which in turn weakens the hold of nucleus on the outermost electron and hence leads to greater tendency to lose an electron. So down the group, electropositivity increases,

Since Francium is the bottom-most element in the group, it should be most electropositive but Fr is radioactive and decays readily. It is not available to us in its elementary form so it is difficult to comment on its ionic properties. So Cesium is the most electropositive element in the periodic table