Although Krypton (Kr) and rubidium (Rb) have nearly the same relative atomic mass, the boiling point of Kr is -152degree celcius whereas that of rubidium is 686 °C. Explain this observation as far as you can in terms of structure and bonding.
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Answer:Kr has a simple atomic structure and consists of lattice of atomes held together by Van Der Waals' forces of attraction, which is arised due to instantaneous dipole-induced dipole attraction.
Rb has a metallic structure and consists of a lattice of positive ions found in a sea of delocalised electrons. Thus, there is strong electrostatic forces of attraction exisiting between delocalised electron cloud and the metal ions.
Since more energy is required to separate the Rb atoms as compared to the Kr atoms due to a larger force of attraction, Rb has a higher b.p than Kr.
