When the elements in group 1 are considered in order from top to bottom, each successive element at standard pressure has
a. a higher melting point and a higher boiling point.
b. a higher melting point and a lower boiling point.
c. a lower melting point and a higher boiling point.
d. a lower melting point and boiling point.

Answer is: d. a lower melting point and boiling point.

Alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

Bond between these elements is metallic bond.

Both the melting and boiling points decrease down the group 1, because the decrease in the strength of each metallic bond.

From top to bottom, atomic radius increase and the distance between the nucleus and delocalized electrons increases, so metallic bond is weaker (attractions fall).

Metallic bond is formed between electrons and positively charged metal ions.