Question

Why are the melting points of alkali metals low as compared to alkaline earth metals?

Answer 1

A substance's melting point (or, more rarely, liquefaction point) is the temperature at which it transitions from solid to liquid state. The solid and liquid phases are in balance at the melting point. A substance's melting point is determined by pressure and is generally given at a standard pressure such as 1 atmosphere or 100 kPa. The freezing point, also known as the crystallisation point, is the temperature at which a liquid changes back into a solid.

Complete answer:
Metallic bonding is a type of chemical bonding that results from the electrostatic attraction between positively charged metal ions and conduction electrons (in the form of an electron cloud of delocalized electrons). It may be characterised as the sharing of free electrons among positively charged ions in a structure (cations). Many physical characteristics of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and brilliance, are determined by metallic bonding.
Alkali metals have a lower melting point than alkaline earth metals. They have two electrons in their valence shell, which causes strong metallic connections to form in the metal crystal lattice for atom binding. Alkali metals, on the other hand, have just one electron in their outermost shell. Alkaline earth metals have greater melting and boiling temperatures than alkali metals, which can be attributed to their smaller size and more closely packed crystal structure, as well as the existence of two valence electrons.
The atomic number of alkaline earths is always one higher than the atomic number of an alkali metal in the same Period. The fact that atomic radius drops across the Period and atomic size increases along a Group, a column of the Periodic Table, is widely known. Metallic bonding should be higher for alkaline earths than for alkali metals. In fact, their differing melting points reflect this.

Note:
Because the electronegativities of the atoms involved in the bonding interaction are so similar even in alloys, metallic bonding is generally non-polar (and, in pure elemental metals, none at all). As a result, metallic bonding is a communal kind of covalent bonding that is very delocalized. Metallic bonding isn't a 'new' form of bonding in the traditional sense. It only explains the bonding in a chunk of condensed matter, such as a crystalline solid, a liquid, or even a piece of glass.