The term 'Soft Silvery Element' is referring to the element Ytterbium, which has an atomic number of 70 and is a member of the lanthanide series. It is a soft, silvery metal that is malleable and ductile. Ytterbium is not found in nature in its elemental form, but is instead found in minerals such as xenotime and euxenite. It is used in various applications, including lasers, X-ray machines, and nuclear reactors.