I read from this reference that rubidium is extracted by reduction of its chloride with calcium or sodium. How is it possible?. Their electronegativities are much higher than rubidium. I think rubidium is far more reactive than either and can not be replaced from its salt by any other metal except cesium. While I have also read that cesium itself is replaced from its chloride by magnesium refer to this. How can a less electropositive metal replace a more electropositive metal from its salt? Are there some factors besides electronegativity, reduction potential and other reaction skills?