Question

which of the alkali metal is having least melting point

Answer 1

The melting points of the alkali metals as a group are lower than those of any other nongaseous group of the periodic table, ranging between 179 °C(354 °F) for lithium and 28.5 °C (83.3 °F) for cesium. Among the metallic elements, only mercury has a lower melting point (−38.9 °C, or −38.02 °F) than cesium.

Answer 2

only mercury has a lower melting point (−38.9 °C, or −38.02 °F) than cesium because of it's different properties otherwise cesium