Question

Why first group elements are soft??

Answer 1

The Group 1 metals are all highly reactive silvery metals that are so reactive to air and moisture that they must be stored under an inert atmosphere or oil. They are all soft and can be cut easily with a knife. Hydrogen is usually placed at the top of the Group but is not a Group 1 metal. The electronic configuration of the metallic elements consist of a lone s-electron outside an inner core of electron corresponding to the previous inert gas. The metals all react with water with ioncreasing severity down the Group. In each case the result is the evolution of hydrogen and formation of alkalime solutions:

M + 2H2O → 2MOH(aq) + ↑H2