Alkali metals are difficult to obtain. Why ?

Alkali metals are soft. Why ?

Alkali metals are kept under kerosene oil. Why ?

Why industrial effluents are more difficult to manage t5han municipal sewage? Nmae a disease that is caused by heavy metal contamination.

Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why ?

Alkali metals show photoelectric effect. Why ?

Why the alkali metals are most suitable for studying the photoelectric emission?