From BCIT.ca: The alkali metals show a decrease in melting points and boiling points due to the weaker metallic bonds between atoms as their size increase down the group.
From AUS-e-TUTE: melting point decreases down the Group as the elements become less metallic in nature
From okstate.edu: As one goes down the Periodic Table, the metallic radius of alkali metals increases. The increase in radius results in much decreased attractive forces between atoms within the liquid metals, resulting in a decrease in heat of vaporization and boiling points [and melting points] because less heat is needed to separate atoms from the liquid [or solid] state within the larger alkali metals. See Web Links to the left for the original sources.
The Bohr model, introduced in 1913 by Niels Bohr was simply the model of the atomic structure; this included the small positively charged nucleus which included the neutrons and protons at the centre and the negatively charged electrons rotating around the nucleus in certain specific orbits by its electromagnetic energy in a circular orbit, similar to the solar system, but with electrostatic forces providing attraction, rather then gravity. In a neutral atom the number of electrons = the number of protons. The arrangement of an atom's energy orbits depends on the number of protons and neutrons in the nucleus and the number of electrons orbiting the nucleus.
The relationship of the alkali metals is simple, as the atomic radius increases the inter molecular forces become weaker as there is less gravitational force acting on the electrons as they are further away from the nucleus (source of gravity), making it easier for them to react/come loose. This is why the melting and boiling points decrease.
All alkali metals are found to be very soft and they have low melting and boiling points. Alkali metals have low binding energy in the metal crystal lattice as these atoms have only one valence electron. This results in the formation of metallic bonds which are not very strong. Also, alkali metals melting and boiling points decrease down the group.
Alkali metals are very reactive, not dense or hard metals, monovalent, with low electronegativities, with low melting and boiling points, react violently with water, form strong bases, etc.
Alkali metals belong to Group 1 of the periodic table. They are highly reactive and readily lose their outermost electron to form positive ions. Alkali metals have low melting and boiling points. They are soft and can be easily cut with a knife. Alkali metals include elements such as lithium, sodium, and potassium.
There is no relation ship. They have the lowest ionization energies.
Alkali metals have relatively low melting points compared to the other metals. Their exact melting points depend on the element itself. But it would be useful to note that their melting points decreases down group I.
Low melting and boiling point
All alkali metals are found to be very soft and they have low melting and boiling points. Alkali metals have low binding energy in the metal crystal lattice as these atoms have only one valence electron. This results in the formation of metallic bonds which are not very strong. Also, alkali metals melting and boiling points decrease down the group.
Alkaline earth metals do not exist , only alkali earth metals
Mercury, all alkali metals (like Sodium) and alkaline-earth metals (like Calcium).
Alkali metals are very reactive, not dense or hard metals, monovalent, with low electronegativities, with low melting and boiling points, react violently with water, form strong bases, etc.
sodium
The melting point of alkali metals is low.
Alkali metals belong to Group 1 of the periodic table. They are highly reactive and readily lose their outermost electron to form positive ions. Alkali metals have low melting and boiling points. They are soft and can be easily cut with a knife. Alkali metals include elements such as lithium, sodium, and potassium.
Th reactivity of alkali metals increases from the top of Group 1A to the bottom
There is no relation ship. They have the lowest ionization energies.
Alkali metals have relatively low melting points compared to the other metals. Their exact melting points depend on the element itself. But it would be useful to note that their melting points decreases down group I.
The melting point of francium is not measured, only supposed by comparison with the melting points of the other alkali metals.